[(x^2+2x-15)/(x^2-4x-45)] / [(x^2+x-12)/(x^2-5x-36)]

= [(x+5)(x-3)/((x-9)(x+5))] / [(x+4)(x-3)/((x-9)(x+4))]

= [x-3)/x-9)] / [(x-3)/(x-9)]
= (x-3)/(x-9) [ (x-9)/(x-3)
= 1 , x ± -5 -4, 3, 9