X^2-2x-15/x^2+x-12*2x^2-6x/x^3+3x^2

Answer 1

Brackets are absolutely essential here.
I am sure you meant

(x^2-2x-15)/(x^2+x-12)*(2x^2-6x)/(x^3+3x^2)

= (x-5)(x+3)/( (x+4)(x-3) ) * 2x(x-3)/( x^2(x+3))
= 2(x-5)/(x(x+4)) or (2x -10)/(x^2 + 4x) , x ≠ ±3,0