如果m加n=3,mn=负3

由于:mn/(m+n)=2则有：mn=2(m+n)则:原式=(3m+3n-5mn)/(-m-n+3mn)=[3(m+n)-5mn]/[-(m+n)+3mn]=[3(m+n)-10(m

(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,

m+mn=-3.（1）n-3mn=8.（2）（1）-（2）得m+mn-n+3mn=-3-8=-11m+4mn-n=-11亲,请您点击【采纳答案】,您的采纳是我答题的动力,

3m-5mn+3n/（-m）+3mn-n=【3（m+n）-5mn】/【3mn-（m+n）】=【3-5mn/（m+n）】/【3mn/（m+n）-1】=【3-5x2】/【3x2-1】=-7/5

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

答：mn/(m+n)=2分子分母同除以mn得：1/(1/n+1/m)=21/m+1/n=1/2(3m-5mn+3n)/(-m+3mn-n)分子分母同除以mn得：=(3/n-5+3/m)/(-1/n+3

先合并同类项,得3(m-n)-6mn+9,代入已知数据,有结果27

由于:mn/(m+n)=2则有：mn=2(m+n)则:原式=(3m+3n-5mn)/(-m-n+3mn)=[3(m+n)-5mn]/[-(m+n)+3mn]=[3(m+n)-10(m+n)]/[-(m

(-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)=-

-MN(M^2N^5-MN^3-N)=-（-6)^3+(-6)^2-(-6)=258

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

m²-mn=21mn-n²=-15所以(m²-mn)+(mn-n²)=21+(-15)m²-mn+mn-n²=21-15所以m²-

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

2[mn+(-3m)]-3(2n-mn)=2mn-6m-6n+3mn=5mn-6m-6n=5mn-6(m+n)m+n=2mn=-3=-15-12=-27

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

(-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

【2m²n-3mn²】÷【mn】=2m-3n

m平方减去n平方=m²-mn+mn-n²=7-2=5m平方减去2mn加n平方=m²-mn-(mn-n²）=7+2=9

m的平方分之一加n的平方分之一=(m^2+N^2)/(NM)^2=((m+N)^2-2mn)/(nm)^2=(25-6)/9=19/9^2为平方

-3*(n/3-n-mn)+2(mn-m/2)=3n-n+3mn+2mn-m=5mn+2n-m由于m+n=-3mn=2得出m=-3-n代入mn=2中有-n(n+3)=2即n^2+3n+2=0即（n+1