(4)4m²-9分之2mn与2m 3分之2m-3

m*2-n*2=4mn两边平方m*4+n*4-2m*2×n*2=16m*2×n*2m*4+n*4=18m*2×n*2两边同除m*2×n*2m*2n*2分之m*4+n*4=18

因为|m-n-2|大于等于0(mn-1）的2次方大于等于0且|m-n-2|与(mn-1）的2次方互为相反数所以m-n-2=0mn-1=0则m-n=2mn=1(-2mn+2m+3n)-(3mn+2n-2

3(m^2+mn)-4(mn-2m^2n)+mn=3m²+3mn-4mn+2m²n+mn=3m²+2m²n=m²(3+2n)

“liljw0924”：二个数的分母分别为4m²-9和2m+34m²-9=（2m）²-3²=（2m+3）×（2m-3）它们的公分母是（2m+3）×（2m-3）通

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

|m-n-2|=-(mn-1)²;所以m-n-2=0;m=n+2;mn-1=0;原式=（-2mn+2m+3n）-（3mn+2n-2m）-（m+4n+mn）=-2mn+2m+3n-3mn-2n

先合并同类项,得3(m-n)-6mn+9,代入已知数据,有结果27

m+n=4则M平方加上2MN加上N平方=16两边乘以1/2则2分之1M的平方+MN+2分之1N的平方等于1/2乘以16等于8

4m²-9=(2m+3)(2m-3)所以最简公分母就是4m²-9所以(2m-3)/(2m+3)=(2m-3)²/(4m²-9)

再答：这个化简一下答案就有了。。。再问：不对你只算了个2m....的值前面还有个条件再答：式子开括号化简完不是m+n-3mn么？那把题目条件带入不就是答案了？再问：我看错了再答：好吧。。。

（2m-n）分之m

2mn/(4m^2-9)(2m-3)/(2m+3)分子分母同时乘(2m-3)=(2m-3)(2m-3)/(2m+3)(2m-3)=(4m^2-12m+9)/(4m^-9)

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

原式=(m²+2mn+n²-4mn)(m²-2mn+n²+4mn)+2m²n²=(m²-2mn+n²)(m²+

3/(2M-N)=3(2M-N)/(2M-N)²2MN/(4M²-4MN+N²)=2MN/(2M-N)²如果不懂,请Hi我,祝学习愉快!

2mn分之4m方—9=n分之2—9=n分之(2-9n)2m—3分之2m+3=3分之(6m-2m-3)=3分之(4m-3)再问：额不好意思啊我不小心手滑打错了应该是2mn分之4m方—9与2m—3分之2m

①2mn/4m^2-9=2mn/[(2m+3)(2m-3)]②2m-3/2m+3=(2m-3)(2m-3)/[(2m+3)(2m-3)]=(2m-3)²/[(2m+3)(2m-3)]③2mn

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

将分式m的2次方+2mn分之n,2n的2次方-mn分之m,m的2次方-4n的2次方分之mn通分后的结果n/(m^2+2mn)=n^2(m-2n)/[mn(m+2n)(m-2n)]m/(2n^2-mn)

n/(m²+2mn)=n/[m(m+2n)]m/(2n²-mn)=-m/[n(m+2n)]2mn/(m²-4n²)=2mn/[(m+2n)(m-2n)]所以n/