已知x-2y=5,则5(x-2y)²-3(x-2y)-60的值为() A.50 B.10 C.210 D.40
问题描述:
已知x-2y=5,则5(x-2y)²-3(x-2y)-60的值为() A.50 B.10 C.210 D.40
答
5(x-2y)²-3(x-2y)-60
=5×5²﹣3×5﹣60
=125﹣15﹣60
=50
∴选A.50你确定吗百分百若-a²b>0,且a0,且a