ACT Math : How to multiply polynomials

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #4 : Polynomials

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Possible Answers:

Correct answer:

Explanation:

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Step 1: Use the distributive property

Step 2: Combine like terms

Example Question #5 : Polynomials

Two positive consecutive whole numbers that are even are both multiples of . The product of the two numbers is . What is the sum of the two integers?

Possible Answers:

Correct answer:

Explanation:

The question provides two positive whole numbers that are each multiples of 6 and also 6 numbers apart. This may be translated into variables, where the first number may be represented by "x" and the second number may be represented as "x+6" given that it is 6 numbers greater than x. 

The problem provides the information that the product of these two numbers is 72. Using the new definitions for the numbers, this may be represented as:

(x)(x+6) = 72

This provides an equation that multiplies two polynomials (one with one term, which is a monomial and one with two terms, which is a binomial) and an ability to solve for what x (the first of the two numbers) may be.

Using FOIL, the result is . This may be rewritten as , which will provide the value of x after factoring. 

, where (-6)(12) will provide the product of -72 and the sum of 12 and -6 will yield 6. The results indicate x as having two possible solutions: x=6 and x=-12. Returning back to the question, the goal is to find two positive numbers. This means that x=-12 is not a viable solution and that x=6 is. Now, revisiting the terms used to redefine the two numbers [x and x+6], x has been calculated. After substituting in the x value for the second term, the second number is 12 (6+6=12). 

The final step of the problem is to solve for the sum of these two numbers:
6+12=18

Example Question #2 : Polynomials

Multiply these polynomials out and expand.

Possible Answers:

Correct answer:

Explanation:

The proper way to multiply polynomials is to essentially apply the distributive property continually.

So  is really the same as , and so on.

Then, simply group together like terms to get the final answer:

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