求人解答这题：已知m^2+3mn=5 m=? n=?

求人解答这题：已知m^2+3mn=5 m=? n=?

有无数解
其中一种
m^2+3mn=5
m(m+3n)=5=1x5
若m=1，n=4/3
若m=5，n= -4/3

已知m²+3mn=5求5m²-[5m²-(2m²-mn)-7mn-5]的值

5m²-[5m²-(2m²-mn)-7mn-5]
=5m^2-(5m^2-2m^2+mn-7mn-5)
=5m^2-5m^2+2m^2-mn+7mn+5
=2m^2+6mn+5
m^2+3mn=5
原式
=2(m^2+3mn)+5
=2×5+5
=15

已知m^3+n^3=10,m^2+n^2=7,求m+n

设m+n=u,mn=v,
则m^2+n^2=u^2-2v=7,
v=(u^2-7)/2,
m^3+n^3=u(u^2-3v)=u[u^2-3(u^2-7)/2]
=u(21-u^2)/2=10,
整理得u^3-21u+20=0,
分解因式得(u-1)(u-4)(u+5)=0,
解得m+n=u=1,4,-5.

已知m^2-mn=3,mn-n^2=5,求3m^2+2mn-5n^2的值，要过程。

∵m²-mn=3,
mn-n²=5,
∴m²-n²=8
∴3m²+2mn-5n²
=3m²-3n²+2mn-2n²
=3(m²-n²)+2(mn-n²)
=3×8+2×5
=34

已知m>n>0，m^2+n^2=4mn,则（m^2-n^2）/mn的值为多少？

由m^2+n^2=4mn得到(m+n)^2=6mn,(m-n)^2=2mn
两式相乘得到(m+n)^2X(m-n)^2=12m^2Xn^2所以（m+n）X（m-n）=2√3mn
除过去就得到原式等于2√3