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Algebra · Algebra

Operations with Monomials

Before you start, make sure you know: Properties of powers (Math 6)
Before you start, make sure you know: Monomials (Math 6)

In a racing video game, every gold coin is worth $5x$ points and every silver coin is worth $2x$ points. If you grab 4 gold coins and 6 silver coins, how many points do you score? To answer that, you need to multiply and add monomials with confidence. Let's build those skills.

Parts of a monomial

A monomial is a single term made of a number and variables multiplied together. Before we operate with monomials, we need names for their parts.

Some problems call the variable part the literal part. It is the same thing.

The monomial −4x²y with its coefficient −4, variable part x²y, and degree 3 labeled. −4x²y coefficient −4 variable part x²y degree 2 + 1 = 3

Two details trip people up. A letter with no exponent has exponent 1, so $y = y^1$. A letter with no number in front has coefficient 1 (or $-1$ if there is a minus sign), so $-a^2b$ has coefficient $-1$.

A plain number like $-5$ is a monomial too. It has no variables, so its degree is $0$.

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To understand how mathematical expressions are built, it is essential to know the parts of a monomial. Complete the requested information for each of the following…

To understand how mathematical expressions are built, it is essential to know the parts of a monomial. Complete the requested information for each of the following monomials:

  1. a) $7x^{3}$
  2. b) $-a^{2}b$
  3. c) $\frac{1}{2}x^{4}y^{2}$
  4. d) $-5$

For each one, state:

  • The coefficient.

  • The literal part.

  • The degree of the monomial.

Solve

Adding and subtracting like terms

You can only add or subtract like terms: terms with exactly the same variables raised to exactly the same exponents. Only the coefficients are different.

$5x^2$ and $-x^2$ are like terms. $5x^2$ and $5x$ are not, because the exponents differ. $3xy$ and $3x$ are not either, because the variables differ.

Combining the like terms 3ab, minus 5ab, and ab by adding the coefficients 3 − 5 + 1 to get −ab. 3ab − 5ab + ab (3 − 5 + 1)ab = −ab ab means 1ab
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In the world of algebra, we can only add or subtract "like terms". Identify which of the following monomials are like terms and group them together: $5x^{2}$, $-3x$,…

In the world of algebra, we can only add or subtract "like terms". Identify which of the following monomials are like terms and group them together:

$5x^{2}$, $-3x$, $\frac{1}{4}x^{2}$, $7y$, $x$, $-x^{2}$, $12x$, $2y$

Solve
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Simplify the following expressions by adding and subtracting the like terms: a) $5a + 3a - 2a$ b) $4x^{2} - x^{2} + 7x^{2}$ c) $3ab - 5ab + ab$ d) $x + x + x + x$

Simplify the following expressions by adding and subtracting the like terms:

  1. a) $5a + 3a - 2a$
  2. b) $4x^{2} - x^{2} + 7x^{2}$
  3. c) $3ab - 5ab + ab$
  4. d) $x + x + x + x$
Solve
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Reduce the following algebraic expression as much as possible by grouping the like terms: $9x^3 - 5x^2 + 4x - 2x^3 + 7x^2 - x + 10$

Reduce the following algebraic expression as much as possible by grouping the like terms:

$9x^3 - 5x^2 + 4x - 2x^3 + 7x^2 - x + 10$

Solve

Multiplying monomials

Unlike addition, you can multiply any two monomials, alike or not.

$$(3x^2)(5x^4) = (3 \cdot 5)(x^{2} \cdot x^{4}) = 15x^6$$

Some problems say "indices" for exponents. The rule is the same.

A rectangle shows why this is useful. Its area is base times height, so multiplying monomials gives areas.

Rectangle with base 5x and height 3x whose area is 3x times 5x, which equals 15x². base 5x height 3x Area = 3x · 5x = 15x²

When a monomial has several variables, handle each letter separately: $(4a^2b)(-3ab^3) = -12a^3b^4$. The $a$'s give $a^{2+1}$ and the $b$'s give $b^{1+3}$.

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Calculate the product of the following monomials. Remember to multiply the coefficients together and add the indices of the same letters: a) $(3x^{2}) \cdot (5x^{4})$ b)…

Calculate the product of the following monomials. Remember to multiply the coefficients together and add the indices of the same letters:

  1. a) $(3x^{2}) \cdot (5x^{4})$
  2. b) $(-2a^{3}) \cdot (4a)$
  3. c) $(\frac{1}{2}x) \cdot (6x^{2})$
  4. d) $(-x^{2}) \cdot (-x^{3})$
Solve
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Calculate the result of the following multiplications of monomials and simplify the literal part using the properties of powers: a) $(4a^2b) \cdot (-3ab^3)$ b)…

Calculate the result of the following multiplications of monomials and simplify the literal part using the properties of powers:

  1. a) $(4a^2b) \cdot (-3ab^3)$
  1. b) $(\frac{1}{2}x^4) \cdot (6x^2)$
  1. c) $(-2z^3) \cdot (-5z^2) \cdot z$
Solve

Dividing monomials

Division works like multiplication, but backward.

$$\frac{15x^3y^2}{3x^2y} = \frac{15}{3}\,x^{3-2}\,y^{2-1} = 5xy$$ The fraction x·x·x over x·x, where two pairs of x cancel and one x remains. x · x · x x · x two pairs cancel, one x is left x³ ÷ x² = x

If the denominator has a variable that the numerator does not, the quotient is not a single monomial. For example, $\dfrac{15m^4n^2}{10m^2}$ simplifies to $\tfrac{3}{2}m^2n^2$, because the $n^2$ has nothing to cancel with and simply stays.

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Work out the following divisions of monomials. Remember to divide the coefficients and subtract the indices of the letters: a) $(12x^{5}) : (3x^{2})$ b)…

Work out the following divisions of monomials. Remember to divide the coefficients and subtract the indices of the letters:

  1. a) $(12x^{5}) : (3x^{2})$
  2. b) $(-10a^{4}) : (5a^{3})$
  3. c) $(15x^{3}y^{2}) : (3x^{2}y)$
  4. d) $(4x^{2}) : (2x^{2})$
Solve
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Simplify the following quotients of monomials. Express the result as a single monomial when possible: a) $\frac{20x^6}{5x^2}$ b) $(-12a^3b^2) : (3a^2b^2)$ c)…

Simplify the following quotients of monomials. Express the result as a single monomial when possible:

  1. a) $\frac{20x^6}{5x^2}$
  1. b) $(-12a^3b^2) : (3a^2b^2)$
  1. c) $\frac{15m^4n^2}{10m^2}$
Solve

Powers of monomials

Use the widget to see how a base grows when the exponent changes.

Fractions work the same way: $\left(-\tfrac12 m^5\right)^3 = \left(-\tfrac12\right)^3 m^{15} = -\tfrac18 m^{15}$.

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Calculate the power of these monomials. Do not forget to raise both the coefficient and the literal part to the given index: a) $(2x^{3})^{2}$ b) $(-3a^{2})^{2}$ c)…

Calculate the power of these monomials. Do not forget to raise both the coefficient and the literal part to the given index:

  1. a) $(2x^{3})^{2}$
  2. b) $(-3a^{2})^{2}$
  3. c) $(x^{4})^{3}$
  4. d) $(-2x)^{3}$
Solve
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Perform the following powers of monomials. Remember that the exponent affects both the coefficient and each of the variables in the literal part: a) $(-3x^4)^2$ b)…

Perform the following powers of monomials. Remember that the exponent affects both the coefficient and each of the variables in the literal part:

  1. a) $(-3x^4)^2$
  1. b) $(2a^2b^3)^4$
  1. c) $(-\frac{1}{2}m^5)^3$
Solve

Combined operations

When an expression has several operations, follow the order of operations (PEMDAS), exactly as with numbers:

  1. Parentheses, then powers.

  2. Multiplication and division, from left to right.

  3. Addition and subtraction: combine like terms.

Three steps for combined operations with monomials: powers first, then multiply and divide, then add and subtract like terms. Step 1 powers Step 2 × and ÷ Step 3 + and − left to right within each step
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Work out the following combined operations with monomials, respecting the order of operations: a) $5x^2 \cdot 2x + 12x^4 : 3x$ b) $3ab \cdot (2a^2b) - (5a^3b^2)$ c)…

Work out the following combined operations with monomials, respecting the order of operations:

  1. a) $5x^2 \cdot 2x + 12x^4 : 3x$
  1. b) $3ab \cdot (2a^2b) - (5a^3b^2)$
  1. c) $(2n^3)^2 - 5n^6 + n^2 \cdot n^4$
Solve
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Perform the following combined operation with monomials, simplifying the result as much as possible. Pay special attention to the order of operations and the rules of…

Perform the following combined operation with monomials, simplifying the result as much as possible. Pay special attention to the order of operations and the rules of powers:

$$ \frac{2}{3}x^2 \cdot (-3x^3)^2 - 5x^5 \cdot (2x^3) + \frac{16x^{10}}{2x^2} $$
Solve

Distributive property and the GCF

When a monomial multiplies a sum or difference, use the distributive property: multiply the monomial by every term inside the parentheses.

$$2x(3x + 4) = 2x \cdot 3x + 2x \cdot 4 = 6x^2 + 8x$$

An area model shows it. A rectangle of height $2x$ and width $3x + 4$ splits into two smaller rectangles.

A rectangle of height 2x and width 3x plus 4 split into two rectangles with areas 6x² and 8x. 3x 4 2x 6x² 8x 2x(3x + 4) = 6x² + 8x

Now run it backward. Factoring out the GCF means pulling out the greatest common factor so that the expression becomes a product.

You can always check by distributing: $6x^2y^2 \cdot 3x^2 = 18x^4y^2$ and $6x^2y^2 \cdot 2y = 12x^2y^3$. ✓

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Reduce the following expression by applying the distributive property and simplifying the resulting like terms: $$ -3ab^2 \cdot (2a^2 - 5ab + b^2) - 2a^2b \cdot (4ab -…

Reduce the following expression by applying the distributive property and simplifying the resulting like terms:

$$ -3ab^2 \cdot (2a^2 - 5ab + b^2) - 2a^2b \cdot (4ab - a) $$
Solve
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Extract the greatest possible common factor in the following algebraic expression. Remember that you must extract both the greatest common factor of the coefficients and…

Extract the greatest possible common factor in the following algebraic expression. Remember that you must extract both the greatest common factor of the coefficients and the common variables with their lowest exponent:

$$ 24x^5y^4z^2 - 36x^3y^6z^3 + 12x^2y^4z^5 $$
Solve

Finding missing monomials and chains of operations

Multiplication and division undo each other, just like with numbers. So to find a missing factor, divide the product by the known factor. To find a missing dividend, multiply.

The same idea works for a quotient. If $N \div (2a) = 5a^3b$, then $N = 5a^3b \cdot 2a = 10a^4b$.

Some problems chain several operations. Do all the multiplications first, then divide, and watch for the degree at the end. Here is an example with three monomials:

$$\frac{(6a^2b)(4ab^3)}{8ab^2} = \frac{24a^3b^4}{8ab^2} = 3a^2b^2$$

The degree of the result is $2 + 2 = 4$.

A "product pyramid" is another chain. Each brick is the product of the two bricks right below it.

A product pyramid: the bottom row 2x, 3x, x² gives 6x² and 3x³ in the middle, and 18x⁵ at the top. 18x⁵ 6x² 3x³ 2x 3x x²
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Find the unknown monomials $M$ and $N$ that make the following equalities true: a) $ (-4x^3y^2) \cdot M = 20x^7y^5 $ b) $ \frac{N}{-3ab} = 6a^2b^3 $ c)…

Find the unknown monomials $M$ and $N$ that make the following equalities true:

  1. a) $ (-4x^3y^2) \cdot M = 20x^7y^5 $
  1. b) $ \frac{N}{-3ab} = 6a^2b^3 $
  1. c) $ (2x^2)^3 : M = -4x $
Solve
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In a strategy video game, the energy of a battalion is calculated by the product of its attack level and its defense level, divided by its fatigue. If we know that:…

In a strategy video game, the energy of a battalion is calculated by the product of its attack level and its defense level, divided by its fatigue. If we know that:

  • Attack: $ 12a^2b^3 $

  • Defense: $ 5a^3b $

  • Fatigue: $ 10ab^2 $

Express the total energy of the battalion as a single monomial and determine its degree.

Solve
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Calculate the value of the resulting monomial at the top of this "product pyramid", where each brick is the result of multiplying the two monomials directly below it:

Calculate the value of the resulting monomial at the top of this "product pyramid", where each brick is the result of multiplying the two monomials directly below it:

× × × −2x 3x² -x³ A B ¿?
Solve

Perimeter with monomials

Perimeter is the distance around a shape, so you add all the outer side lengths. If the sides are monomials, you end up adding like terms.

A rectangle with length 3x and width x whose perimeter is 3x + x + 3x + x = 8x. 3x 3x x x Perimeter 3x + x + 3x + x = 8x

For an irregular shape, add every outer side. If a side isn't labeled, find it from the labeled ones. For instance, two parallel sides of a rectangle always have the same length.

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Find the algebraic expression that represents the perimeter of the following rectangular plot intended for a school garden. Once you have the expression, simplify it…

Find the algebraic expression that represents the perimeter of the following rectangular plot intended for a school garden. Once you have the expression, simplify it fully by adding its like terms.

3x x
Solve
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Find the simplified algebraic expression that represents the perimeter of the following plot intended for a play area in a park:

Find the simplified algebraic expression that represents the perimeter of the following plot intended for a play area in a park:

5x x 2x 2x 2x 2x
Solve

Area with monomials

The area of a rectangle is base times height, so you multiply monomials. For a shape with a hole, or a frame, use subtraction:

$$\text{shaded area} = \text{outer area} - \text{inner (white) area}$$ A square of side 5x with a smaller white square of side 2x removed; the shaded frame has area 25x² − 4x². 5x 2x 25x² − 4x² = 21x²

Another way to find an area is to split the shape into rectangles, find each area, and add them. Use whichever way the figure suggests.

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Calculate the expression that represents the area of the shaded region in the following figure, knowing that the side of the outer square measures $4x$ and the side of…

Calculate the expression that represents the area of the shaded region in the following figure, knowing that the side of the outer square measures $4x$ and the side of the inner white square measures $x$:

4x x
Solve
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A design company manufactures aluminum frames for tablet screens. The design follows the proportions shown in the following figure, where all measurements are expressed…

A design company manufactures aluminum frames for tablet screens. The design follows the proportions shown in the following figure, where all measurements are expressed in terms of a variable $x$. Find the monomial that represents the total surface area of the frame (the shaded zone).

Area = ? 6x 4x 4x 2x
Solve

Volume and word problems

The volume of a cube with edge $s$ is $s^3$. That is a power of a monomial! For a box, volume = length $\times$ width $\times$ height, which is a product of three monomials.

A cube with edge one half x inches has volume one eighth x cubed, so four such cubes have volume one half x cubed. edge ½x in. V = (½x)³ = ⅛x³ 4 cubes: 4 · ⅛x³ = ½x³ in.³

When joining identical cubes, first find the volume of one cube, then multiply by the number of cubes.

Word problems work the same way. Translate each phrase into a monomial. "Per" quantities multiply, and "total" quantities often add. Check for like terms at the end.

Back to the start: 4 gold coins are worth $4 \cdot 5x = 20x$ points, and 6 silver coins are worth $6 \cdot 2x = 12x$ points. They are like terms, so the total is $20x + 12x = 32x$ points.

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In a racing video game, for every gold coin collected you get $5x$ points and for every silver coin you get $2x$ points. If in a game a player has collected 4 gold coins…

In a racing video game, for every gold coin collected you get $5x$ points and for every silver coin you get $2x$ points.

If in a game a player has collected 4 gold coins and 6 silver coins:

  1. a) Write the monomial that represents the total points from the gold coins.
  2. b) Write the monomial that represents the total points from the silver coins.
  3. c) Add both monomials to find the total points for the game.
Solve
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In a reforestation campaign, each volunteer plants $3x$ trees in the morning and $2x$ trees in the afternoon. If there is a total of $y$ volunteers, write the simplified…

In a reforestation campaign, each volunteer plants $3x$ trees in the morning and $2x$ trees in the afternoon. If there is a total of $y$ volunteers, write the simplified algebraic expression that represents:

  1. a) The total number of trees planted by a single volunteer in one day.
  1. b) The total number of trees planted by all the volunteers in a week (7 days).
Solve
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Calculate the monomial that represents the volume of a geometric solid formed by joining 5 identical cubes, where the edge of each cube measures $ \frac{2}{3}x^2 $ feet.…

Calculate the monomial that represents the volume of a geometric solid formed by joining 5 identical cubes, where the edge of each cube measures $ \frac{2}{3}x^2 $ feet. Express the final result in a simplified form.

2 3 x² × 5
Solve

Summary

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