Question

What is the coefficient of x^4 in(x^2−x−2)^7?

Answer 1

x^14-7 x^13+7 x^12+49 x^11-91 x^10-161 x^9+357 x^8+363 x^7-714 x^6-644 x^5+728 x^4+784 x^3-224 x^2-448 x-128