作业帮解二元一次方程组3(x+y)-4(x-y)=4 x+y/2+x-y/6=1
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解二元一次方程组3(x+y)-4(x-y)=4 x+y/2+x-y/6=1
解二元一次方程组3(x+y)-4(x-y)=4 x+y/2+x-y/6=1
解二元一次方程组3(x+y)-4(x-y)=4 x+y/2+x-y/6=1
3(x + y) - 4(x - y) = 4 ①
x + y/2 + x - y/6 = 1 ②
由①得
7y - x = 4 ③
由②得
2x + y/2 - y/6 = 1
2x + 3y/6 - y/6 = 1
2x - y/6 = 1
12x - y = 6 ④
③ + ④ × 7得
83x = 46
x = 46/83
把 x = 46/83代入 ③得
7y - 46/83 = 4
7y = 4 + 46/83
7y = 378/83
y = 378/581
∴ 原方程组的解为
x = 46/83
y = 378/581
如果原方程是“3(x + y) - 4(x - y) = 4 x + y）/2 + （x - y）/6 = 1 ”的话,可以作如下解答.
3(x + y) - 4(x - y) = 4 ①
（x + y）/2 + （x - y）/6 = 1 ②
② × 6得
3(x + y) + (x - y) = 6 ③
③ - ①得
5(x - y) = 2
x - y = 2／5 ④
把x - y = 2／5代入①得
3(x + y) - 4 × 2／5 = 4
3(x + y) = 48／5
x + y = 16／5 ⑤
④ + ⑤得
2x = 18／5
x = 9／5
把x = 9／5代入 ④得
9／5 - y = 2／5
y = 9／5 - 2／5
y = 7／5
∴ 原方程组的解为
x = 9／5
y = 7／5