m+n=8,mn=15求值
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原式=-2mn+6m²-m²+5(mn-m²)-2mn,=-2mn+6m²-m²+5mn-5m²-2mn,=mn,当m=1,n=-2时,原式
(m²+n²+mn)/(m²-n²)分子分母同除以n²=[(m/n)²+1+m/n]/[(m/n)²-1]=[(7/8)²
2(mn+m)-[-(3n-mn)-m]+mn =2mn+2m+3n-mn+m+mn =2mn+3m+2n =2mn+3(m+n) ∵m+n=3,mn=-2 ∴2(mn+m)-[-(3n-m
(m+n)(m^2-mn+n^2)+(m-n)(m^2+mn+n^2)=m^3+n^3+m^3-n^3=2m^3=-2立方和公式:m^3+n^3=(m+n)(m^2-mn+n^2)立方差公式:m^3-
m/(m-n)-n/(m+n)+2mn/(m²-n²)=[m(m+n)-n(m-n)+2mn]/(m²-n²)=(m²+n²)/(m
-2(mn-3m²)-[m²-5(mn-m²)+2mn]=-2mn+6m²-m²+5(mn-m²)-2mn=-2mn+6m²-m&
-2(mn-3m²)-[m²-5(mn-m²)+2mn]=-2mn+6m²-m²+5mn-5m²-2mn=mn=1x-2=-2
3m^2-mn/9m^2-6mn+n^2=m(3m-n)/(3m-n)^2=m/(3m-n)=3n/(9n-n)=3/8
把括号都拆开即可原式=-2mn+6m²-m²+5(mn-m²)-2mn=-2mn+6m²-m²+5mn-5m²-2mn=mn当m=1、n=-
原式=-3/2mn-13/4m-7/2n=45/4-65/4+21/4=1/4
2(mn-3m*)-5(mn+m*)=2mn-6m²-5mn-5m²=-3mn-11m²=-m(3n+11m)=2(3×1-11×2)=-38
-(mn-3)+3(-mn-1)-5mn=-mn+3-3mn-3-5mn=-9mn=-9*2*23=-414
m²+n²+mn=(m²+2mn+n²)-mn=(m+n)²-mn=8²-15=64-15=49
-2(mn-3m^2)-m^2+5(mn-m^2)+2mn=-2mn+6m^2-m^2+5mn-5m^2+2mn=5mn当m=1,n=-2时原式=5×1×(-2)=-10再问:谢谢。你是个好人啊
[(-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^
.(m+n)(m的平方-mn+n的平方)+(m-n)(m的平方+mn+n的平方)=m³+n³+m³-n³=2m³=2x(-1)³=-2如果本
=(mn)^2-4-(m-n)^2=(mn+m-n)(mn-m+n)-4把m=2n=0.5代入=(1+1.5)*(1-1.5)-4=-5.25
m^2+n^2=(m+n)^2-2mn=10^2-2x24=100-48=52(m-n)^2=(m+n)^2-4mn=10^2-4x24=100-96=4
2m的平方-3mn-n的平方-2mn-2m的平方+5mn-2n+1=-n的平方-2n+1=-1/4+1+1=7/4
[(3m-n)^2-(3m-n)(3m+n)-4mn]/(2n)=[(9m²+n²-6mn)-(9m²-n²)]/(2n)=(9m²+n²-