Question

x-y=4 4x+2y=-1二元一次方程用代入法怎么解

Answer 1

x-y=4化为x=4+y
带入4x+2y=-1
4（4+y）+2y=-1
16+2y=-1
y=-17/6
x=7/6

Answer 2

x-y=4 x=4+y 代入 4x+2y=-1
4*（4+y）+2y=-1 --> 16+6y=-1 -->y=-17/6
再将 y=-17/6 代入 原式 x-y=4 --> x=4+(-17/6) x=7/6