解方程组2x+3y=13,5x-7y=-11

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解方程组2x+3y=13,5x-7y=-11

解方程组2x+3y=13,5x-7y=-11
解方程组2x+3y=13,5x-7y=-11

解方程组2x+3y=13,5x-7y=-11
2x+3y=13(1)
5x-7y=-11(2)
(1)*5-(2)*2得29y=87 y=3 ,代入(1)x=2

2x+3y=13 10x+15y=65
5x-7y=-11 10x-14y=-22 相加得 y=3 x=2

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