Question

解二元一次方程1.x+y=3 2.x-y=-5 3.x=3y 4.4x-3y=17 5.3x+y=10 x-y=2 3x

Answer 1

1.两式相加：x=2.5 y=0.5

2.上式×2+下式：x=0 y=5

3.上式代入下式：y=1 x=3

4.下式代入上式：x=2 y=-3

5.上式×2+下式：x=2.7 y=1.9