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Math 7 · Mathematics
Algebra · Algebra

Monomials

Before you start, make sure you know: Monomials (Math 6)
Before you start, make sure you know: Operations with monomials (Math 6)

A game in an app store earns a profit of $7x^2y$ dollars per download. Before you can do any math with an expression like this, you have to be able to read it: which part is the number, and which part is the letters?

What is a monomial?

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

Diagram of the monomial 7x²y showing the coefficient 7, the variable part x²y, and the degree 2 + 1 = 3. 7 x²y coefficient variable part degree = 2 + 1 = 3 (y has exponent 1, even if it isn't written)

Not every expression is a monomial. $x + 2$ has two terms, and $\frac{3}{x}$ has a variable in the denominator, so neither one is a monomial.

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In an app store, the profit for each download of a game is expressed by the monomial $7x^2y$. Identify the following elements of this expression: Coefficient: Literal…

In an app store, the profit for each download of a game is expressed by the monomial $7x^2y$. Identify the following elements of this expression:

  • Coefficient:

  • Literal part:

  • Degree of the monomial:

Solve
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In a math app, a bot has misclassified some monomials. Your task is to correct the following table by identifying the coefficient, the literal part and the degree of…

In a math app, a bot has misclassified some monomials. Your task is to correct the following table by identifying the coefficient, the literal part and the degree of each one. If you find any errors in the bot's classification, write it correctly:

Monomial Coefficient Literal part Degree
$-5x^2y$ $5$ $x^2y$ $2$
$\frac{3}{4}ab^3c$ $3$ $ab^3c$ $4$
$-x^4$ $-1$ $x$ $4$
$7$ $7$ None $1$
Solve

Like terms

$5x^2$ and $-2x^2$ are like terms. $5x^2$ and $5x$ look similar, but the exponents don't match, so they are not like terms. The order of the letters doesn't matter: $2a^2b$ and $5ba^2$ are like terms.

Like terms 5x² and −2x² share the variable part x²; 5x² and 5x do not. like terms 5x² −2x² same variablepart: x² NOT like terms 5x² 5x differentvariable part
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We are organizing an inventory of robotics parts. Group the following monomials into pairs that are like terms: $5x^2$, $-3ab$, $x$, $\frac{1}{2}ab$, $-2x^2$, $8x$

We are organizing an inventory of robotics parts. Group the following monomials into pairs that are like terms:

$5x^2$, $-3ab$, $x$, $\frac{1}{2}ab$, $-2x^2$, $8x$

Solve

Evaluating a monomial

To find the value of a monomial, substitute a number for each variable (use parentheses for negative numbers) and then calculate. Powers come first, then multiplication.

Step-by-step evaluation of −5x² at x = −1, giving −5. M(x) = −5x²substitute x = −1 −5 · (−1)²= −5 · 1 = −5
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Calculate the numerical value of the monomial $M(x) = -5x^2$ for the indicated values of the variable: a) $x = 2$ b) $x = -1$ c) $x = 0$

Calculate the numerical value of the monomial $M(x) = -5x^2$ for the indicated values of the variable:

  1. a) $x = 2$
  2. b) $x = -1$
  3. c) $x = 0$
Solve
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Calculate the numerical value of the following monomials for the values of the variables indicated in each case: a) $P(x, y) = -3x^2y$ for $x = -2$, $y = 5$ b)…

Calculate the numerical value of the following monomials for the values of the variables indicated in each case:

  1. a) $P(x, y) = -3x^2y$ for $x = -2$, $y = 5$
  1. b) $Q(a, b) = \frac{2}{3}a^3b^2$ for $a = 3$, $b = -1$
Solve

Adding and subtracting monomials

$$4x + 2x - x = (4 + 2 - 1)x = 5x$$ Blocks showing x² + x² + x simplifies only to 2x² + x, because x² and x are not like terms. x² x² + x = 2x² + x can't be combined into one monomial: x² and x are not like terms

When a coefficient is a fraction, add it like any fraction: $8x^2y + \tfrac{1}{2}x^2y = \left(8 + \tfrac{1}{2}\right)x^2y = 8\tfrac{1}{2}\,x^2y$.

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Reduce the following algebraic expressions by adding and subtracting the like terms: a) $4x + 2x - x$ b) $5a^2 - 3a^2 + 7a^2$ c) $3ab + ab - 2ab$

Reduce the following algebraic expressions by adding and subtracting the like terms:

  1. a) $4x + 2x - x$
  2. b) $5a^2 - 3a^2 + 7a^2$
  3. c) $3ab + ab - 2ab$
Solve
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A content creator analyzes the growth of their social networks. The number of "Likes" on their photos is given by the monomial $8x^2y$, and the number of "Shares" by…

A content creator analyzes the growth of their social networks. The number of "Likes" on their photos is given by the monomial $8x^2y$, and the number of "Shares" by $3x^2y$. During the last month, they have received extra views equivalent to $\frac{1}{2}x^2y$.

Calculate the simplified algebraic expression that represents the total interaction by adding the three concepts.

Solve

Multiplying monomials

x squared times x cubed written as five factors of x, giving x to the fifth power. x² · x³ (x · x) · (x · x · x) = x · x · x · x · x = x⁵ 2 + 3 = 5 factors of x
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Perform the following multiplications of monomials and simplify the result: a) $3 \cdot (5x^4)$ b) $(-2x^2) \cdot (4x)$ c) $(3a) \cdot (2b)$

Perform the following multiplications of monomials and simplify the result:

  1. a) $3 \cdot (5x^4)$
  2. b) $(-2x^2) \cdot (4x)$
  3. c) $(3a) \cdot (2b)$
Solve

Dividing monomials

x to the fifth divided by x squared: two factors of x cancel, leaving x cubed. x · x · x · x · x x · x = x · x · x = x³ exponents: 5 − 2 = 3

When the exponents are equal, everything cancels. For example, $\dfrac{9x^3}{3x^3} = 3x^0 = 3$. Any nonzero number or variable to the power $0$ equals $1$, so $-2x^0 = -2$.

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In a strategy video game, your base's energy increases according to the following operation of monomials. Reduce the expression to a single monomial: $$(12x^5 \cdot…

In a strategy video game, your base's energy increases according to the following operation of monomials. Reduce the expression to a single monomial:

$$(12x^5 \cdot 3x^2) : (9x^4)$$

What is the degree of the resulting monomial?

Solve

Powers of monomials

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Simplify the following expression that combines powers and divisions of monomials: $$\frac{(-2a^3b)^2 \cdot 5ab^4}{10a^4b^3}$$

Simplify the following expression that combines powers and divisions of monomials:

$$\frac{(-2a^3b)^2 \cdot 5ab^4}{10a^4b^3}$$
Solve
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Simplify the following combined expression with monomials as much as possible, applying the properties of powers and the order of operations: $$\frac{(-3x^2y^3)^2 \cdot…

Simplify the following combined expression with monomials as much as possible, applying the properties of powers and the order of operations:

$$\frac{(-3x^2y^3)^2 \cdot (2x^4y)^3}{(-6x^3y^2)^2}$$

Express the result as a single monomial.

Solve
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Calculate the degree of this "chained" monomial and simplify it to its simplest form: $$P(x) = x \cdot (2x^2)^3 : \left( \frac{1}{4}x^4 \right) + (-5x^3) \cdot (-2x^0)$$…

Calculate the degree of this "chained" monomial and simplify it to its simplest form:

$$P(x) = x \cdot (2x^2)^3 : \left( \frac{1}{4}x^4 \right) + (-5x^3) \cdot (-2x^0)$$

Are the terms resulting from the sum like terms? Justify your answer.

Solve

Missing monomials and exponents

When one piece of an equation is missing, use the inverse operation:

  • missing addend: subtract the known one from the total;

  • missing factor: divide the product by the known factor;

  • missing divisor: divide the dividend by the quotient.

A product pyramid: the top brick 6x² is the product of the two bricks below it, 2x and 3x. 6x² 2x 3x 2x · 3x = 6x²

The answer to (3) is $4x^3y^2$.

Unknown exponents. Some problems hide an exponent in a letter, like $M = -5x^ay^b$. Two facts help:

  • The degree in $x$ (some problems call it the relative degree with respect to $x$) is just the exponent of $x$.

  • If two powers of the same base are equal, their exponents are equal: $2^a = 8 = 2^3$ means $a = 3$.

When two conditions give two equations, write them both, then substitute one into the other. For example, if $a + b = 6$ and $a = 2b$, then $2b + b = 6$, so $b = 2$ and $a = 4$. Exponents of a monomial are whole numbers, so if yours isn't, re-read the conditions and check your work.

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Complete the gaps with the necessary monomial so that the equalities are correct: a) $7x^3y + \dots \dots = 10x^3y$ b) $(-2ab^2) \cdot (\dots \dots) = 12a^3b^2$ c)…

Complete the gaps with the necessary monomial so that the equalities are correct:

  1. a) $7x^3y + \dots \dots = 10x^3y$
  1. b) $(-2ab^2) \cdot (\dots \dots) = 12a^3b^2$
  1. c) $\frac{15x^4y^2}{\dots \dots} = 3x^2y$
Solve
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In the following "product pyramid", each brick is the result of multiplying the two monomials directly below it. Complete the empty spaces by finding the monomials $A$,…

In the following "product pyramid", each brick is the result of multiplying the two monomials directly below it. Complete the empty spaces by finding the monomials $A$, $B$ and $C$.

× × × 36x⁷y⁵ A 6x³y³ 3x²y B C
Solve
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It is known that the numerical value of the monomial $M(x, y) = -5x^a y^b$ is $-160$ when $x=2$ and $y=2$. Furthermore, it is known that the relative degree with respect…

It is known that the numerical value of the monomial $M(x, y) = -5x^a y^b$ is $-160$ when $x=2$ and $y=2$. Furthermore, it is known that the relative degree with respect to the variable $x$ is twice the relative degree with respect to $y$.

Find the exponents $a$ and $b$, justifying the steps taken.

Solve

From words and shapes to monomials

Algebra is a language. To translate a phrase, work from the inside out.

The side lengths of a figure can be monomials too. A regular polygon has equal sides, so its perimeter is (number of sides) $\times$ (side).

A regular octagon with each side x inches; its perimeter is 8x. x in. 8 sides, each x in. P = 8x
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Translate the following phrases into algebraic language using a single monomial: a) Twice the cube of a number $x$. b) Half the product of two numbers $a$ and $b$. c)…

Translate the following phrases into algebraic language using a single monomial:

  1. a) Twice the cube of a number $x$.
  2. b) Half the product of two numbers $a$ and $b$.
  3. c) Three times the square of the distance $d$.
Solve
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Observe the following regular hexagon whose side measures $x$ feet. Write the monomial that represents its perimeter and calculate its value if each side measured $4,5$…

Observe the following regular hexagon whose side measures $x$ feet. Write the monomial that represents its perimeter and calculate its value if each side measured $4,5$ inches.

x
Solve

Area with monomials

The area of a rectangle is length $\times$ width, so the area of a rectangle with sides $5x$ and $3x$ is $5x \cdot 3x = 15x^2$. For a shaded region, find the area of the whole shape and subtract the part that is cut out.

A 5x by 3x rectangle with an x by x square cut from the top-right corner. x 5x 3x area = 5x · 3x − x · x

If the pieces you subtract are not like terms, the answer stays as two terms. For example, $9x^2 - 4y^2$ can't be combined. That is fine: just leave it.

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Find the monomial that expresses the area of the following rectangle intended for a "gaming" zone in a shopping mall:

Find the monomial that expresses the area of the following rectangle intended for a "gaming" zone in a shopping mall:

GAMING ZONE Area = ? 5x 3x
Solve
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Find the monomial that represents the area of the following shaded zone, which is part of the design of a new skate park. Express the result in the most simplified form…

Find the monomial that represents the area of the following shaded zone, which is part of the design of a new skate park. Express the result in the most simplified form possible.

5x² 3y
Solve
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Calculate the monomial that represents the perimeter and the monomial that represents the shaded area of the following composite figure (a large square of side $3x$ from…

Calculate the monomial that represents the perimeter and the monomial that represents the shaded area of the following composite figure (a large square of side $3x$ from which four identical small squares of side $y$ have been cut out at its corners):

3x y y

Reduce the expressions as much as possible.

Solve

Factoring out the GCF

Sometimes you want to go backward from a sum to a product. If every term shares a factor, you can pull out the greatest common factor (GCF).

An area model: a rectangle of height 2x split into parts of width 3x and 2 with areas 6x² and 4x, so 6x² + 4x = 2x(3x + 2). 6x² 4x 3x2 2x 2x(3x + 2) = 6x² + 4x

Fraction coefficients. Write all coefficients over a common denominator, find the GCF of the numerators, and keep the denominator.

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Observe the following figure composed of two adjoining rectangles. a) Write the monomial that represents the area of each rectangle separately. b) Write the monomial…

Observe the following figure composed of two adjoining rectangles.

  1. a) Write the monomial that represents the area of each rectangle separately.
  2. b) Write the monomial that represents the total area.
  3. c) Extract the common factor in the expression for the total area.
A₁ A₂ 4a 2x 3y
Solve
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Extract the greatest possible common factor (greatest common factor of the terms) in the following algebraic expression. Pay special attention to the fractional…

Extract the greatest possible common factor (greatest common factor of the terms) in the following algebraic expression. Pay special attention to the fractional coefficients:

$$\frac{4}{9}a^5b^2 - \frac{8}{27}a^3b^4 + \frac{2}{3}a^3b^2$$
Solve

Modeling with monomials

Monomials describe real situations such as costs and patterns. When a total cost is a sum of terms, splitting it among friends means dividing every term.

Patterns. A figure pattern grows by the same amount each step. Look at the sequence $5, 9, 13, \dots$ It grows by $4$ each time, so the rule starts with $4n$. At $n = 1$, $4n = 4$ but the term is $5$, so add $1$: the rule is $4n + 1$.

Note that $4n + 1$ is not a monomial. It is a sum of two unlike terms. Still, it is built from a monomial, and you evaluate it the same way.

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Three friends rent a pickleball court. The total cost is given by the algebraic expression $C(t, l) = 6t + 2l$, where $t$ is the time in hours and $l$ is the number of…

Three friends rent a pickleball court. The total cost is given by the algebraic expression $C(t, l) = 6t + 2l$, where $t$ is the time in hours and $l$ is the number of paddles rented.

  1. a) If they decide to divide the cost equally, write the algebraic expression that represents what each one must pay.
  1. b) If a fourth friend joins the group, the total cost of the paddles increases (there are now $l+1$) and the cost is divided by four. Write the new expression for the individual payment.
  1. c) If the playing time is $1,5$ hours and each one rents their own paddle, how many dollars does each of the three original friends save when the fourth player joins?
Solve
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Observe the following sequence of figures formed by small squares. The first term ($n=1$) has 4 squares, the second ($n=2$) has 7, and the third ($n=3$) has 10. a)…

Observe the following sequence of figures formed by small squares. The first term ($n=1$) has 4 squares, the second ($n=2$) has 7, and the third ($n=3$) has 10.

n = 1 4 squares n = 2 7 squares n = 3 10 squares
  1. a) Determine the monomial that represents the number of squares in terms of the position $n$, knowing that the relationship is linear (a monomial in $n$ plus a constant term).
  1. b) How many squares will the figure in position $n=150$ have?
  1. c) If a figure has 91 squares, what position $n$ does it occupy in the sequence?
Solve

Back to the start: in the monomial $7x^2y$, the coefficient is $7$, the variable part is $x^2y$, and the degree is $2 + 1 = 3$.

Summary

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