m+n=5,mn=14,则(3m-2n)-(-5n+mn)

问题描述:

m+n=5,mn=14,则(3m-2n)-(-5n+mn)

(3m-2n)-(-5n+mn)
=3m-2n+5n-mn
=3m+3n-mn
=3(m+n)-mn
=3*5-14
=1