若x²-y²=6 x+y=-3则(x-y)²=?
问题描述:
若x²-y²=6 x+y=-3则(x-y)²=?
答
x²-y²=6
(x+y)(x-y)=6
∵x+y=-3
∴x-y=-2
(x-y)²=(-2)²=4