2/(m+n)+3/(m-n)=3/2,1/(m+n)-9/(m-n)=-1,求m,n的值
问题描述:
2/(m+n)+3/(m-n)=3/2,1/(m+n)-9/(m-n)=-1,求m,n的值
答
2/(m+n)+3/(m-n)=3/2,①
1/(m+n)-9/(m-n)=-1②
令1/(m+n)=a,1/(m-n)=b
2a+3b=3/2③
a-9b=-1④
③×3+④,得
7a=7/2
a=1/2
b=(a+1)/9=1/6
所以
m+n=2
m-n=6
m=(2+6)÷2=4
n=2-4=-2高手,佩服!尤老师,我再请教: 4/(x+y)与(x+y)/(xy)哪个大?怎么计算?谢谢!