=(x-1)(x-6)(x+2)(x-3)+56 乘式中1,4 2,3 结合
=(x^2-4x+3)(x^2-4x-12)+56 将x^2-4x看做一项
=(x^2-4x)^2-9(x^2-4x)+20
=(x^2-4x-4)(x^2-4x-5)
=(x^2-4x-4)(x-5)(x+1)
=(x-1)(x-6)(x+2)(x-3)+56 乘式中1,4 2,3 结合
=(x^2-4x+3)(x^2-4x-12)+56 将x^2-4x看做一项
=(x^2-4x)^2-9(x^2-4x)+20
=(x^2-4x-4)(x^2-4x-5)
=(x^2-4x-4)(x-5)(x+1)