先化简,再求值:(m-n)•(m+n)+(m+n)的平方-2m的平方,-搜答案-智慧作业帮

（m+n）²+（m+n）（m-3n）=（m+n)(m+n+m-3n)=（m+n)(2m-2n)=2(m+n)(m-n)=2(-1+1)(-1-1)=0

原式=4m²-n²+2mn+n²-4m²=2mn=2×(-1/2)×2013=-2013

3m+4n-[2m+(5m-2n)-3n]=3m+4n-2m-5m+2n+3n=-4m+9n=-4*1+9*2=-4+18=14再问：m=1么？？再答：m=1不是你写的嘛

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

8m^2-(6m^2+15m^2n)÷3m+m(n-1)=8m^2-2m-5mn+mn-m=8m^2-4mn-3m代入m=2,n=1得出原式=8*2^2-4*2*1-3*2=32-8-6=18

=1+√N+√(MN)=1+√2+√6

（m-1/4n)(m+1/4n)-3(m+1/4n)^2其中m=-1,n=4=m²-n²/16-3m²-3n²/16-3mn/2=-2m²-n

(m+n)(m一n)一(一2m+3n)(一2m一3n),=(m+n)(m一n)一(2m-3n)(2m+3n),=m^2-n^2-(4m^2-9n^2)=8n^2-3m^2(m=1,n=一1)=8-3=

3m^2-4(-2n^2+4m^2)-2(7n^2+5m^2)=3m^2+8n^2-16m^2-14n^2-10m^2=-23m^2-6n^2m=+1n=-1-23-6=-29

[(-3mn)^2*m^3-2m^2(3mn^2)^3*0.5n]/(-3m^2n)^2=[9*m^2*n^2*m^3-2*m^2*27*m^3*n^6*0.5n]/(9*m^4n^2)=m-3mn^

(5m-2m)+(3n-8n)=3m-6n=0.8

3m+4n-[2m+(5m-2n)-3n]=3m+4n-(2m+5m-2n-3n)=3m+4n-(7m-5n)=3m+4n-7m+5n=-4m+9n代入m=2,n=1/2得原式=-7/2你有问题也可以

（mn-m²)÷(m²-2mn+n²)/mn·(m²-n²)/m²=m(n-m)×mn/(m-n)²×(m+n)(m-n)/m&#

8m(m+n)²-2m(m-n)²=2m(4(m+n)²-(m-n)²)=2m(2m+2n+m-n)(2m+2n-m+n)=2m(3m+n)(3n+m)再把m=

2m-(n+1)+（m²-2mn+n²-1）/m-n-1=2m-n-1+(m-n+1)(m-n-1)/(m-n-1)=2m-n-1+m-n+1=3m-2n=6-6=0

=6m-4n=2(3m-2n)再答：代入m,n得:2（7.5-2.4）=2×5.1=10.2

8m2-5m（-m+3n）+4m（-4m-52n）=8m2+5m2-15mn-16m2-10mn=-3m2-25mn，当m=2，n=-1时，原式=-3×22-25×2×（-1）=38．

原式=4m²-n²+mn+2n²-4m²-4mn-n²=-3mn

[(3m-n)^2-(3m-n)(3m+n)-4mn]/(2n)=[（9m²+n²-6mn）-（9m²-n²）]/(2n)=(9m²+n²-

(2m+n)(2m-n)+n(2m+n)-8m²n²÷(2n)m=-1/24m²-n²+2mn+n²-4mn=-1/28m²-4mn=-1