Question

3. Simplify (12x3 – 8x2) – (3x3 + 9x2 + x – 7).
Responses

A. 9x3 + x2 – x + 7
A. 9 x 3 + x 2 – x + 7

B. 9x3 – 17x2 – x + 7
B. 9 x 3 – 17 x 2 – x + 7

C. 15x3 – 17x2 – x – 7
C. 15 x 3 – 17 x 2 – x – 7

D. 15x3 + x2 + x – 7

Answer 1

Subtract the second polynomial term-by-term:

(12x^3 – 8x^2) – (3x^3 + 9x^2 + x – 7)
= 12x^3 – 8x^2 – 3x^3 – 9x^2 – x + 7
= (12x^3 – 3x^3) + (–8x^2 – 9x^2) + (–x) + 7
= 9x^3 – 17x^2 – x + 7

Answer: B.