Digital PSAT Math Practice Question 346: Answer and Explanation

Question: 346

If -16 - 6x + x² = x² - abx - 8b, where a and b are constants, what is the value of a?

• A. –6
• B. –2
• C. 3
• D. 5

Correct Answer: C

Explanation:

(C) The different terms on the two sides of the equation equal each other. So $-16=-8b$, $-6x=-abx$, and $x^2=x^2$. Why? This occurs because the constants must equal each other, the terms with an x must equal each other, and the terms with an $x^2$ must equal one another. Since $-16=-8b$, $b=2$. Plug in 2 for b in the second equation and cancel out the $-x$ to solve for a: