已知2y-x=5,则5(x-2y)方-3(x-2y)-60的值是?A.80 B.10 C.210 C.40

问题描述:

已知2y-x=5,则5(x-2y)方-3(x-2y)-60的值是?A.80 B.10 C.210 C.40

(x-2y)方=(2y-x)方=5的平方 x-2y=-(2y-x)=-5
(5(x-2y)方-3(x-2y)-60
=5*5的平方-3*(-5)-60
=80
所以应该选A、80