(X^2-2X-3)(X^2-2X-8)-36

来源:百度知道 编辑:UC知道 时间:2024/05/22 09:07:10
请问这道题答案多少
因式分解

设t=x^2-2x-3
则原式=t(t-5)-36
=t^2-5t-36
=(t-9)(t+4)
=(x^2-2x-12)(x^2-2x+1)
=(x-1)^2(x^2-2x-12)

连个"="都没怎么算啊?

(X^2-2X-3)(X^2-2X-8)-36
设x^2-2x=k
=(k-3)(k-8)-36
=k^2-8k-3k+24-36
=k^2-11k-12
=(k-12)(k+1)
=(x^2-2x-12)(X^2-2x+1)
=(x^2-2x-12)(x-1)^2

(X^2-2X-3)(X^2-2X-8)=36

(X^2-2X-3)=y
(y-5)y=36
y=9 x=更号13+1