1.若m-n=4,mn=1,求（9-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)的值

1.9-2mn+2m+3n-3mn-2n+2m-m-4n-mn=9-6mn+3m-3n=9-6mn+3(m-n)=9-6+12
=15
2.因为:2a^2+3a+1=6,即:2a^2+3a=5,
所以:原式=3(2a^2+3a)+5=3*5+5=15+5=20.
3.周长=2(2a+3b)+2(a+b)-2(a-b)-(a-b)=4a+6b+2a+2b-2a+2b-a+b
=3a+11