用加减法解方程组,5x+3(y-5)=12,4x-7(5-y)=5

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用加减法解方程组,5x+3(y-5)=12,4x-7(5-y)=5

用加减法解方程组,5x+3(y-5)=12,4x-7(5-y)=5
用加减法解方程组,5x+3(y-5)=12,4x-7(5-y)=5

用加减法解方程组,5x+3(y-5)=12,4x-7(5-y)=5
5x+3(y-5)=12 (1)
4x-7(5-y)=5 (2)
(1)×7-(2)×3
35x+35(y-5)-12x+35(5-y)=84-15
23x=69
所以
x=3
y=(12-5x)/3+5=4