6x^4+7x^3-36x^2-7x+6
=(6x^4+x^3-x^2)+(6x^3+x^2-x)+(-36x^2-6x+6)
=x^2(6x^2+x-1)+x(6x^2+x-1)-6(6x^2+x-1)
=(6x^2+x-1)(x^2+x-6)
=(2x+1)(3x-1)(x-2)(x+3).