Digital PSAT Math Practice Question 218: Answer and Explanation

Question: 218

Which of the following is a solution to the equation below?

(x - 3)² - 81 = 0

• A. 12
• B. 11
• C. 9
• D. 8

Correct Answer: A

Explanation:

(A) First, FOIL the (x - 3)² term in the equation to obtain:

x² - 6y + 9 - 81 = 0. Then you can combine like terms:

x² - 6y - 72 = 0. This factors to

(x - 12)(x + 6) = 0. Setting each term equal to 0 tells you that x can either equal 12 or - 6. Only 12 is an answer choice, choice (A).