将4(x-y)²-9(x-y)²+5(y-x)²-4(x-y)²按(x-y)²合并同类型得【数学

问题描述:

将4(x-y)²-9(x-y)²+5(y-x)²-4(x-y)²按(x-y)²合并同类型得【数学
A.-4x平方+4y² B.-14x²+14y² C.-14(x-y)² D.-4(x-y)²

4(x-y)²-9(x-y)²+5(y-x)²-4(x-y)²
=4(x-y)²-9(x-y)²+5(x-y)²-4(x-y)²
=(4-9+5-4)(x-y)²
=-4(x-y)²