(3)f(X1,.,xn)=X2+2x3+.+Xm-七， 1 2 解：A 2 x x n x x x x x n x n f 1 1 2 2 3 1 (3) ( , , )  = + ++ − 1 0 0 0 0 2 1 1 0 0 0 2 2 1 0 0 0 0 2 1 0 0 0 0 2 1 0 0 0 0 2 A     =   解：