若x+y=-z,則(x^2-y^2)+(xz-yz)的值是___

若x+y=-z,則(x^2-y^2)+(xz-yz)的值是___

x+y=-z
(x^2-y^2)+(xz-yz)
=(x+y)(x-y)+z(x-y)
=-z(x-y)+z(x-y)
=0