Question

Rút gọn A = ( x + y + z )³ - ( x + y - z )³ - ( x - y + z )³ - ( -x + y + z )³

Answer 1

A=(x+y)^3+3(x+y)^2*z+3(x+y)*z^2+z^3-(x+y)^3+3(x+y)^2*z^2-3(x+y)*z^2+z^3-(x-y+z)^3+(x-y-z)^3

=6(x+y)^2+2z^3+(x-y)^3-3(x-y)^2*z+3(x-y)*z^2-z^3-(x-y)^3-3*(x-y)^2*z-3*(x-y)*z^2-z^3

=6(x+y)^2+2z^3-6(x-y)^2-2z^3=0