已知:m-n=7,mn=2,求5m-3mn-5n+2的值
问题描述:
已知:m-n=7,mn=2,求5m-3mn-5n+2的值
答
5m-3mn-5n+2
=5(m-n)-3mn+2
=5*7-3*2+2
=35-6+2
=31