题目应是：已知-m+2n=2,求5(m-2n)²+6n-3m-3的值

已知-m+2n=2
m-2n=-2,
5(m-2n)²+6n-3m-3的值
=5(-2)²+3(-m+2n)-3
=5*4+3*2-3
=20+6-3
=23