f = 2(x1-x2)^2-x2^2-2x2x3-4x3^2
= 2(x1-x2)^2-(x2+x3)^2-3x3^2
= 2y1^2-y2^2-3y3^3应该是2y1^2-y2^2-3y3^2吧，怎么从x变成y的呵呵 又写错了 看来今天应该停下了y1=x1-x2y2=x2+x3y3=x3这还问, 等我出错是不是