5x-2y=5x-4y=1x=1 y=0mx+5y=4m=45x+ny=1n =无解5x-2y=23x-4y=1x=5 y=1mx+5y=45m+5=4m=-1/55x+ny=125+n=1n =-24
5x-2y=23 (1)x-4y=1(2)(1)×2-(2)9x=45x=5y=(5x-5)/2=10代入另两个m-50=425+10n=1所以m=54n=-12/5