只写对x1的偏导数即可.f(x)=a11x1^2+2a12x1x2+2a13x1x3+.+2a1nx1xn+.,后面的项与x1无关,因此af/ax1=2a11x1+2a12x2+2a13x3+...+2a1nxn=2(Ax)的第一行.
于是f'(x)=2Ax.
只写对x1的偏导数即可.f(x)=a11x1^2+2a12x1x2+2a13x1x3+.+2a1nx1xn+.,后面的项与x1无关,因此af/ax1=2a11x1+2a12x2+2a13x3+...+2a1nxn=2(Ax)的第一行.
于是f'(x)=2Ax.