Answer:
6
Step-by-step 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.