Question

Let $f(x) = x^3 + 3x ^2 + 4x - 7$ and $g(x) = -7x^4 + 5x^3 +x^2 - 7$. What is the coefficient of $x^3$ in the sum $f(x) + g(x)$?

Answer 1

6

Explanation:

Adding the two polynomials gives

(x^3 + 3x^2 + 4x - 7) + (-7x^4 +5x^3 + x^2 - 7) =

-7x^4 + (x^3 + 5x^3) + (3x^2 + x^2) + 4x + (-7-7) =

- 7x^4 + 6x^3 + 4x^2 + 4x -14

The x^3 term is 6x^3, so the desired coefficient is 6.