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Prep 2 SS · Mathematics
Algebra · Algebra

Monomials

Before you start, make sure you know: Operations with monomials (Secondary Year 2)
Before you start, make sure you know: Operations with powers (Secondary Year 3)

A clothing store in Guadalajara calculates its profit from the number of customers and how much each one spends. A delivery drone in CDMX uses battery power depending on its speed and the load it carries. In economics, almost nothing depends on just one letter. The monomial is the simplest building block for writing those dependencies, and mastering its rules is the first step before working with polynomials and equations. At the end we will see how a profit changes when you double the customers and cut the spending in half.

Coefficient, literal part, and degree

Diagram breaking down the monomial −5x²y³ into its coefficient −5, its literal part x²y³, and the sum of exponents that determines its degree 5. − 5 x²y³ coefficient literal part degree = 2 + 3 = 5
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To understand how mathematical expressions work in economics, it is essential to identify their components. Complete the requested information for the following…

To understand how mathematical expressions work in economics, it is essential to identify their components. Complete the requested information for the following monomials:

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

For each of them, state the coefficient, the literal part and the degree.

Solve
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An architect is designing a rectangular window for a bank office. The dimensions of the window are given as a function of a variable $x$ as shown in the image. Write the…

An architect is designing a rectangular window for a bank office. The dimensions of the window are given as a function of a variable $x$ as shown in the image. Write the monomial that represents the area of the window.

Area = ? 5x 3x
Solve

Like monomials: addition and subtraction

Two monomials are like monomials when they have exactly the same literal part (the same letters with the same exponents). You can only add or subtract like monomials, and you do it by adding their coefficients. It is like money: you can put together 3 bills of $\$20$ with 2 bills of $\$20$, but you can't mix them with coins without changing units.

Sum of like monomials, which share the same literal part, versus unlike monomials, whose sum stays indicated. like monomials: add the coefficients 5x²y + (−2x²y) = 3x²y different literal parts 5x²y + 3xy² cannot be simplified
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In user interface design, variables are sometimes used to define the size of elements. In order to add or subtract two elements, their monomials must be like terms.…

In user interface design, variables are sometimes used to define the size of elements. In order to add or subtract two elements, their monomials must be like terms.

Determine which of the following pairs of monomials are like terms:

  1. a) $5x^2y$ and $-2x^2y$
  1. b) $3ab^2$ and $3a^2b$
  1. c) $-x$ and $\frac{1}{2}x$
  1. d) $4z^3$ and $4z^2$
Solve
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Simplify the following expressions by collecting like terms, just as you would when calculating the total balance of income and expenses for a small shop: a)…

Simplify the following expressions by collecting like terms, just as you would when calculating the total balance of income and expenses for a small shop:

  1. a) $3x^2 + 5x^2 - 2x^2$
  1. b) $7ab - 3ab + ab$
  1. c) $4x^3 - 5x + 2x^3 + 9x$
Solve
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Find the error in the following simplification process carried out by a student and write the correct solution step by step: Original expression:…

Find the error in the following simplification process carried out by a student and write the correct solution step by step:

Original expression: $\displaystyle \frac{8x^5 + 4x^5}{2x^2}$

Student's Step 1: $\displaystyle \frac{12x^{10}}{2x^2}$

Student's Step 2: $\displaystyle 6x^5$

Explain which law of indices or property of monomials the student applied incorrectly in each step.

Solve

Product and quotient of monomials

To multiply monomials, you multiply the coefficients and, in the literal part, you add the exponents of each matching letter. To divide, you divide the coefficients and subtract the exponents.

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Carry out the following monomial multiplications. Remember that to multiply monomials, you multiply the coefficients and add the exponents of the same variables: a)…

Carry out the following monomial multiplications. Remember that to multiply monomials, you multiply the coefficients and add the exponents of the same variables:

  1. a) $(4x^2) \times (3x^5)$
  1. b) $(-2a^3b) \times (5ab^2)$
  1. c) $(\frac{1}{2}x) \times (6x^2y)$
Solve
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Divide the following monomials and simplify the result. Keep in mind that to divide monomials, you divide the coefficients and subtract the exponents of the powers with…

Divide the following monomials and simplify the result. Keep in mind that to divide monomials, you divide the coefficients and subtract the exponents of the powers with the same base:

  1. a) $\frac{12x^7}{3x^2}$
  1. b) $\frac{-20a^4b^3}{5a^2b}$
  1. c) $\frac{8x^3y^2}{2x^3y}$
Solve
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In a packaging design company, cardboard boxes in the shape of a rectangular prism are being designed. The length of the base is three times the width ($x$) and the…

In a packaging design company, cardboard boxes in the shape of a rectangular prism are being designed. The length of the base is three times the width ($x$) and the height of the box is half the width.

  1. Express the perimetre of the base of the box as a monomial in terms of the variable $x$.

  2. Express the total volume of the box as a monomial. State the coefficient, the literal part and the degree of the monomial obtained.

3x x x/2
Solve

Power of a monomial

Raising a monomial to the power $k$ raises the coefficient to $k$ and multiplies the exponent of each letter by $k$.

Steps for the power of a monomial: (2x²y)³ becomes 2³x⁶y³ and ends as 8x⁶y³. (2x²y)³ 2³x⁶y³ 8x⁶y³
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Determine whether the following statements are true or false, justifying your answer with examples or counterexamples: a) The sum of two monomials of degree 3 is always…

Determine whether the following statements are true or false, justifying your answer with examples or counterexamples:

  1. a) The sum of two monomials of degree 3 is always another monomial of degree 3.
  2. b) The degree of the monomial resulting from multiplying a monomial of degree $n$ by another of degree $m$ is $n + m$.
  3. c) When dividing two monomials with the same literal part, the result is always a real number (degree 0).
Solve
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Given the monomials $M = \frac{2}{3}x^2y^3$, $N = \frac{1}{2}x^2y^3$ and $P = -\frac{5}{6}x^2y^3$: 1. Perform the operation $M - N + P$ and simplify the resulting…

Given the monomials $M = \frac{2}{3}x^2y^3$, $N = \frac{1}{2}x^2y^3$ and $P = -\frac{5}{6}x^2y^3$:

  1. Perform the operation $M - N + P$ and simplify the resulting coefficient.

  2. Multiply the previous result by the monomial $Q = 12xy$. State the final degree of the expression obtained.

Solve
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Simplify the following algebraic expression until reducing it to a single monomial. Keep in mind the properties of powers and work carefully with fractional…

Simplify the following algebraic expression until reducing it to a single monomial. Keep in mind the properties of powers and work carefully with fractional coefficients:

$$L(x, y) = \frac{(2x^3y^2)^3 \times (\frac{1}{2}x^2y^2)^2}{\sqrt{16x^8y^{10}}} : (x^2y^2)^2$$

State the degree of the resulting monomial.

Solve

Finding parameters: equating monomials

Sometimes a monomial has unknown letters in the coefficient or in the exponents, like $k\,a^{n+1}b^{2m-3}$, and the problem gives you information to find them. The key is this: two monomials are equal only if they have the same coefficient and the same exponents on each letter. So each equality of monomials turns into ordinary equations: one for each exponent and one for the coefficient. Relative degrees also give equations: if the relative degree with respect to $a$ is three times the one with respect to $b$, the exponent of $a$ is $3$ times that of $b$.

When the problem gives two conditions on two coefficients, you end up with a system of two equations in two unknowns. You solve it by substitution: you solve for one letter in one equation and substitute it into the other.

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Find two monomials $M_1$ and $M_2$ such that their sum is $10x^2y^3$ and their product is $16x^4y^6$. Are these monomials like terms? Justify your answer based on the…

Find two monomials $M_1$ and $M_2$ such that their sum is $10x^2y^3$ and their product is $16x^4y^6$. Are these monomials like terms? Justify your answer based on the definition of like terms and the results obtained.

Solve
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Consider the monomial $M(a, b) = k \times a^{n+1} \times b^{2m-3}$. It is known that when this monomial is divided by $Q(a, b) = \frac{1}{3}a^2b^2$, a monomial of degree…

Consider the monomial $M(a, b) = k \times a^{n+1} \times b^{2m-3}$. It is known that when this monomial is divided by $Q(a, b) = \frac{1}{3}a^2b^2$, a monomial of degree 5 with coefficient 12 is obtained. Furthermore, in the resulting monomial, the degree with respect to the variable $a$ is three times the degree with respect to the variable $b$.

Calculate the values of the parameters $k$, $n$ and $m$.

Solve
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Determine the values of the real coefficients $p$ and $q$ so that the product of the monomials $A(x) = p x^{n+2}$ and $B(x) = q x^{2n-1}$ is equal to the monomial…

Determine the values of the real coefficients $p$ and $q$ so that the product of the monomials $A(x) = p x^{n+2}$ and $B(x) = q x^{2n-1}$ is equal to the monomial $C(x) = 15x^{10}$. It is also known that if we add $A(x)$ and $B(x)$ when $n=3$, we obtain a binomial whose numerical value for $x=1$ is 8.

Solve the system to find $p$ and $q$.

Solve

Monomials that model real situations

A drone's energy use, a company's profit, or the volume of a box are often written as a monomial in several variables. Substituting values gives the specific result; and to find out what happens when you double or reduce a variable, it is enough to use the properties of powers, without redoing the whole calculation.

Diagram of how the profit B changes when x doubles and y is cut in half: the factor x² is multiplied by 4 and y by 1/2, so B is multiplied by 2. B(x, y) = 0.45x²y x → 2x y → y/2 x² is multiplied by 4 and y by 1/2: the profit is multiplied by 2

Go back to the beginning: if a store doubles its customers and each one spends half as much, the profit in the model $0.45x^2y$ does not stay the same, it doubles! That is because $x$ carries more weight (it is squared).

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A financial analyst models the profits of a tech startup using the monomial $B(x, y) = 0.45x^2y$, where $x$ represents the number of active users (in thousands) and $y$…

A financial analyst models the profits of a tech startup using the monomial $B(x, y) = 0.45x^2y$, where $x$ represents the number of active users (in thousands) and $y$ the average marketing spend per user (in pesos).

  1. Calculate the numerical value of the profit if the company has $20,000$ users ($x=20$) and the marketing spend is $200$ pesos per user ($y=200$).

  2. If the number of users doubles and the marketing spend is halved, what happens to the total profit? Justify your answer using the properties of monomials.

Solve
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In an artificial intelligence data center, the volume of air needed to cool a server rack is modeled by the product of three critical dimensions. The height is a…

In an artificial intelligence data center, the volume of air needed to cool a server rack is modeled by the product of three critical dimensions. The height is a monomial $A(x, y) = \frac{3}{4}x^2y$, the width is $B(x, y) = \frac{8}{9}xy^3$ and the depth is $C(x, y) = \frac{1}{2}x^3y^2$.

Obtain the resulting monomial that defines the total volume $V(x, y)$ of the rack and determine its coefficient, its literal part and its overall degree. What would happen to the degree of the monomial if we doubled the exponent of the variable $x$ in the depth?

A(x,y) = 3/4 x²y B(x,y) = 8/9 xy³ C(x,y) = 1/2 x³y²
Solve
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It is desired to distribute a government grant of $S$ pesos among a number of municipalities $N$ that depends on the population. The total grant is defined by the…

It is desired to distribute a government grant of $S$ pesos among a number of municipalities $N$ that depends on the population. The total grant is defined by the monomial $S(a, b) = 2\,880a^6b^4$ and the number of municipalities by $N(a, b) = (2a^2b)^2$.

Calculate the monomial that represents the amount in pesos that each municipality will receive. If due to a budget adjustment, the amount per municipality must be reduced to a quarter, what would be the new resulting monomial?

Solve

Summary

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