Question

已知,方程组[mx-y=n,3x+ny=m]的解为[x=1,y=2],求2m-n/m+2n的值?

Answer 1

将解x=1,y=2代入方程组得

m-2=n

3+2n=m

所以3+2(m-2)=m

3+2m-4=m

m=1,所以n=-1

(2m-n)/(m+2n)

=(2+1)/(1-2)

=-3