因式分解：6x的三次方+11x的二次方—7x—15

6x^3+11x^2-7x-15
=6x^3+9x^2+2x^2+3x-10x-15
=3x^2(2x+3)+x(2x+3)-5(2x+3)
=(2x+3)(3x^2+x-5)