二元一次方程

x=-2
y=3

No steps...too simple

x+y=1------------(1)
x+2y=4----------(2)
(2)-(1) y =3
把y=3代入
x=-2

x+y=1
x=1-y ------- 1

x+2y=4 ------ 2

put 1 into 2

(1-y)+2y=4
y+1=4
y=3 ------ 3

Put 3 into 2,
x+2x3=4
x+6=4
x=-2

x=-2
y=3

it is a easy question

x+y=1
x=1-y ------- 1

x+2y=4 ------ 2

put 1 into 2

(1-y)+2y=4
y+1=4
y=3 ------ 3

Put 3 into 2,
x+2x3=4
x+6=4
x=-2

x=-2
y=3

For these problem, the best way to do it is to find out x in terms of y or y in terms of x ....... x= ?y +? or y=?x + ?
then put it into the other given formula.... and u'll find one of the answers...

Finally just plug it into any formula u had... and u'll get the other answer....

2007-01-25 08:18:28 補充：
the third one who answer the question:how can you get 1=x yif x=1 and y=1.5.....??

2007-01-25 08:19:11 補充：
sorry.... he has just deleted the ans.......

2007-01-26 08:36:03 補充：
this guy just copy my ans. and post it....
i've showed the steps and everything in my answer.....
i dun know what the 發問者 is thinking.....

x+y=1.........1
x+2y=4........2
從2
x=2y-4..........3
從3代入1
2y-4+y=1
3y=5
y=5分之3
從y=-1代入3
x=2(5分之3)-4
x=5[2(5分之3)]-4(5)
x=6-20
x=-14
錯更~~
比你參考