解方程组2x+3y=13,5x-7y=-11
问题描述：
解方程组2x+3y=13,5x-7y=-11
答
2x+3y=13两边乘以5得10x+15y=65 5x-7y=-11两边乘以2得10x-14y=-22 左式减右式得29y=87,y=3 再代入原方程中得x=2
答
2x+3y=13 10x+15y=65
5x-7y=-11 10x-14y=-22 相加得 y=3 x=2
答
2x+3y=13(1)
5x-7y=-11(2)
（1）*5-(2)*2得29y=87 y=3 ,代入（1）x=2