求方程组 3m-4n=7 9m-10n+23=0

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求方程组 3m-4n=7 9m-10n+23=0
求方程组 3m-4n=7 9m-10n+23=0

求方程组 3m-4n=7 9m-10n+23=0
3m-4n=7 则3m=7+4n
代入得:
9m-10n+23=0
3×(7+4n)-10n+23=0
21+12n-10n+23=0
2n= -44
n= -22
则3m=7+4×(-22)
3m= -81
m= -27

3m-4n=7 ①
9m-10n+23=0 ②
由①×3-②得
-2n=44,n=-22
将n=-22带入①得,m=-27

3m-4n=7 ① 9m-10n+23=0 即:9m-10n=-23 ②
②-①×3 得:
9m-10n-(9m-12n) =-23-21
12n-10n=-44
2n=-44
n=-22
将n=-22带入① 得m=-27
综上:m=-27 n=-22