(x-5)2+(6-x)2 后面的2是平方吗?
(x-5)^2+(6-x)^2=4
2x^2-22x+57=0
(x-5)(6-x)=-x^2+11x-30=-(x^2-11x+30)=-1/2*(2x^2-22x+60)=-1/2*(2x^2-22x+57+3)
=-1/2*(2x^2-22x+57)-3*1/2
=-1/2*0-3/2
=-3/2