Question

因式分解：(2x-7)(2x+5)(x^2-9)-91

Answer 1

(2x-7)(2x+5)(x^2-9)-91

=(2x-7)(x+3)(2x+5)(x-3)-91

=(2x^2-x-21)(2x^2-x-15)-91

=(2x^2-x)^2-36(2x^2-x)+315-91

=(2x^2-x)^2-36(2x^2-x)+224

=(2x^2-x-8)(2x^2-x-28)

=(2x+7)(x-4)(2x^2-x-8)