(x^2-4x-12)(x^2-4x+3)+56
问题描述：
(x^2-4x-12)(x^2-4x+3)+56
答
(x^2-4x-12)(x^2-4x+3)+56
=(x^2-4x﹚²-9(x^2-4x﹚+20
=(x^2-4x-4﹚(x^2-4x-5﹚
=(x²-4x-4﹚﹙x+1﹚﹙x-5﹚
答
(x^2-4x-12)(x^2-4x+3)+56
=（X^2-4X)^2-9(x^2-4x)-36+56
=（X^2-4X)^2-9(x^2-4x)+20
=(x^2-4X-4)(x^2-4x-5)
答
令a=x^2-4x
原式=(a-12)(a+3)+56
=a²-9a-36+56
=a²-9a+20
=(a-4)(a-5)
=(x^2-4x-4)(x^2-4x-5)
=(x^2-4x-4)(x-5)(x+1)