x+1/3=2y,2x-y=20

问题描述:

x+1/3=2y,2x-y=20

x + 1 / 3 = 2 y ①
2 x - y = 20 ②
② × 2 得:4 x - 2 y = 40 ③
把 ① 代入 ③ 得:
4 x - (x + 1 / 3)= 40
4 x - x - 1 / 3 = 40
3 x = 40 + 1 / 3
3 x = 121 / 3
x = 121 / 9
代入 ① 得:
121 / 9 + 1 / 3 = 2 y
2 y = 124 / 9
y = 62 / 3
∴ x = 121 / 9 ,y = 62 / 9