原式=x^2+4x+4-10x-20+25 =x^2-6x+9 =(x-3)^2所以x1=x2=3
(x+2)2-10(x-2)+25=0x2+4x+4-10x+20+25=0x2-6x=-49(x-6)x=-49x-6=-49/xx=-49+6x/x
解：（x+2-5)²=0 （x-3)²=0 x=3
