(x-y+z)²等于多少

(x-y+z)²等于多少
(x-y+z)²等于多少

(x-y+z)²等于多少
(x-y+z)^2
=(x-y)^2+2z(x-y)+z^2
=x^2-2xy+y^2+2xz-2yz+z^2
=x^2+y^2+z^2-2(xy+xz+yz).

x²+y²+z²+2xz-2xy-2yz

原式=[(x-y)+z]²
=(x-y)²+2(x-y)z+z²
=x²-2xy+y²+2xz-2yz+z²