3 m n-4 n-m=2,4m 3 n=2

m+n=2mn=-42（mn-3m）-3(2n-mn)=2mn-6m-6n+3mn=5mn-6(m+n)=-20-12=-32

(2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)先去括号=2mn+2m+3n-3mn-2n+2m-m-4n-mn合并同类项=-2mn+3m-3n=-2mn+3(m-n)把m-n=2,

解（-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn）=-2mn+2m+3n-3mn-2n+2m-m-4n-mn=-2mn-3mn-mn+2m+2m-m+3n-2n-4n=-6mn+3

已知﹣3xy的n＋1次方与5x的m＋3y四次方是同类项则1=m+3n+1=4解得m=-2n=3所以3n四次方-6m3n-4n四次方＋2nm3次方=-n^4-4m^3n=-3^4-4*(-2)^3*3=

先合并同类项,得3(m-n)-6mn+9,代入已知数据,有结果27

原式=mn（m2-9）=mn（m+3）（m-3）．故答案为：mn（m+3）（m-3）

解1/m-1/n=4两边乘以mn得：n-m=4mn∴(2m-3mn-2n)/(m-2mn-n)=[2(m-n)-3mn]/[(m-n)-2mn]=[2×(-4mn)-3mn]/[(-4mn)-2mn]

(-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)=-2mn+2m+3n-3mn-2n+2m-m-4n-mn=(-2mn-3mn-mn)+(2m+2m-m)+(3n-2n-4n)=-

（9-2mn+2m+3n)-(m+4n+mn）=9-2mn+2m+3m-m-4n-mn=9-mn+(m-n)=9-(-1)+4=14

4(-2mn+2m+3n)-2(3m+5n-mn)=-8mn+8m+12n-6m-10n+2mn=-6mn+2m+2n=-6mn+2(m+n)=-6*(-1)+2*3=6+6=12

-2mn+2m+3n-3mn-2n+2m-4n-m-mn=-6mn+3m-3n=-6mn+3(m-n)=6+9=15

根据题意绝对值和完全平方非负所以mn-1=0m-n-2=0mn=1m-n=2（-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)=-2mn+2m+3n-3mn-2n+2m-m-4n-m

m+n=-2mn=-4则2(mn-3m)-3(2n-mn)的值=2mn-6m-6n+3mn=5mn-6(m+n)=5*(-4)-6(-2)=-20+12=-8

原式=-2mn+2m+3n-3mn-2n+2n-m-4n-mn=-6mn+m-n=-6×2+4=-8

已知mn=-1,m-n=4则(-2mn+m+n)-(3mn+5n-5m)-(m+4n-3mn)=-2mn+m+n-3mn-5n+5m-m-4n+3mn=-2mn+5m-8n=2+20-3n=22-3n

3(m^2n+mn)-4(mn-2m^2n)+mn.=3m^2n+3mn-4mn+8m^2n+mn.=11m^2n.

(-m-4n-mn)-(2mn-2m-3n)-(3mn+2n-2m)=-m-4n-mn-2mn+2m+3n-3mn-2n+2m=3m-3n-6mn=3(m-n)-6mn=3×3-6×(-3)=9+18

原式化简=mn²+2mn+4mn²-3mn=5mn²-mn注：[(mn²﹚#(2mn)]=mn²+2mn因为m#n=m+n同理后面的一样带入值运算得1

2（mn-3m)-3（2n-mn）=2mn-6m-6n+3mn=2mn+3mn-6(m+n)=32

m^2-mn=14mn-3n^2=-2m^2+3mn-3n^2=(m^2-mn)+3mn-3n^2+mn=1+4mn-3n^2=1-2=-1