(x-1)^2-10(x-1)+25=0(2)x^2-20-21=0

问题描述:

(x-1)^2-10(x-1)+25=0
(2)x^2-20-21=0

(x-1)^2-10(x-1)+25=0
[(x-1)-5]²=0
(x-6)²=0
x1=x2=6
(2)x^2-20x-21=0
(x-21)(x+1)=0
x1=21,x2=-1