一條數學題！！～急！！ｔｈｘ～

(1)*60: 12(x+2)-20(9-x)=15(y-6)
12x+24-180+20x=15y-90
32x-15y=66......(3)
(2)*8: 8(x+2)-2x-y=2(x+13)
8x+16-2x-y=2x+26
4x-y=10......(4)
(3)-(4)*8:(32x-15y)-8(4x-y)=66-8(10)
32x-15y-32x+8y=-14
-7y=-14
y=2
Sub y=2 into (4)
4x-2=10
x=3
Therefore x=3,y=2

Check:
(1): L.H.S.
=(3+2)/5-(9-3)/3
=5/5-6/3
=1-2
=-1
R.H.S.=(2-6)/4=-1
Therefore for (1), L.H.S.=R.H.S.
(2): L.H.S.=3+2-[2(3)+2]/8
=5-8/8
=4
R.H.S.=(3+13)/4
=16
Therefore for (2),L.H.S.=R.H.S.
Therefore x=3,y=2 satisfy the equation.

2006-10-29 10:24:26 補充：
二樓的答案同一樓好似完全一樣......係咪抄架?

from 2
8x+16-2x-y=2x+26
4x-10=y.......3
put 3 into 1
(x+2)/5 - (9-x)/3 = (4x-10-6)/4
(3x+6-45+5x)/15=(4x-16)/4
(8x-39)/15=x-4
8x-39=15x-60
7x=21
x=3.........4
put 4 into 3
4(3)-10=y
y=2
所以 x=3 , y=2
希望幫到你 求你選我最佳答案

求下你

唔該!!!!!!


唔該!!!!!!

from 2
8x+16-2x-y=2x+26
4x-10=y.......3
put 3 into 1
(x+2)/5 - (9-x)/3 = (4x-10-6)/4
(3x+6-45+5x)/15=(4x-16)/4
(8x-39)/15=x-4
8x-39=15x-60
7x=21
x=3.........4
put 4 into 3
4(3)-10=y
y=2
所以 x=3 , y=2

睇唔睇得明呀??