若m-n=4,mn=-1,求代数式(9-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+

mn)的值。
2025-05-20 22:40:28
推荐回答(1个)
回答1:

(9-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)
=9-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=9-6mn+3m-3n
=9-6mn+3(m-n)
=9+6+12
=27