SAT Math Multiple Choice Question 129: Answer and Explanation
9. What is the value of (2x2 + 4x + 8) - (2x2 - 4x + 7) ?
- A. 4x2 + 8x + 15
- B. 2x2 + x + 1
- C. 8x + 1
- D. 8x + 15
Correct Answer: C
C To solve this question, rearrange the expressions (2x2 + 4x + 8) and (2x2 - 4x + 7) in order to place the similar terms next to each other. Doing so will give you 2x2 - 2x2 + 4x - (-4x) + 8 - 7 (remember to distribute the negative sign for each of the terms in the second expression). Simplifying this new expression will yield 0 + 8x + 1, or 8x + 1, (C). Another way to approach this question would be to plug in a simple number for x, such as x = 2, and match your target value with the values in the answer choices.