用代入消元法解方程组, 2x+3y=40 x-y=-5

题目

用代入消元法解方程组, 2x+3y=40 x-y=-5

答案

x-y=-5 则x=y-5,代入2x+3y=40,得
2(y-5)+3y=40
则5y=50
解得y=10
代入x=y-5,得x=5