f(xj,x2,.,xn)=ax +2a2xx2 +..+2ainxxn+ax, +...+ 2a2nX,xn+ax +.+2antgxn+...+a..x.?=dx*+2ax +2axx=dx*+2x2a*)+22ag*x-2?85.2标准形V§5.2 标准形 2 1 2 11 1 12 1 2 1 1 ( , , , ) 2 2 n n n f x x x a x a x x a x x = + + + 2 22 2 2 2 2 n n + + + a x a x x 2 33 3 3 3 2 n n + + + a x a x x2 nn n + + a x 2 11 1 1 1 2 2 2 2 n n n j j ij i j j i j a x a x x a x x = = = = + +   2 11 1 1 1 2 2 2 2 n n n j j ij i j j i j a x x a x a x x = = = = + +  