y=2x^2-4x-1y=2(x-1)^2-3(y+3)/2=(x-1)^2因为x小于等于1,所以x-1小于等于0.故而[(y+3)/2]^(0.5)=-(x-1)（左边为是根式,大于0）x=1-[(y+3)/2]^(0.5)置换xy,反函数为y=1-[(x+3)/2]^(0.5)^表示次方,^0.5等于是开根号....