F2-Math

1.
(1)x3 3x+9y=3
-)(2) 3x+y=11
------------------------
8y=-8
y=-1
2.
(1)x3 3x+12y=39
-)(2) 3x+2y=9
------------------------------
10y=30
y=3
3.
(1)x3 6x-9y=15
-)(2)x2 6x+4y=28
--------------------------
-13y=-13
y=1
4.
(1)x2 12x+10y=22
+)(2)x5 25x-10y=15
-----------------------------
37x =37
x=1
5.
(1)x6 24x-30y=36
-)(2) 24x-9y=1
--------------------------------
-21y=35
y=-5/3

2008-02-21 00:15:02 補充：
我只計了加減消元法的直式，之後將我計到的答案(y=?/x=?)代入方程（１）／（２）就可以！

1.{x+3y=1 -------(1)
3x+y=11--------(2)
(1) x 3 - (3): 8y = -8
y = -1,
sub into (1): x +3(-1) = 1
x = 4

2.{x+4y=13 ----------(1)
3x+2y=9 -----------(2)
(1) - 2 x (2): -5x = -5
x = 1
sub into (1): 1+4y=13
y = 3

3.{2x-3y=5 -------------(1)
3x+2y=14 ----------(2)
3 x (1) - 2 x (2): -13y = -13
y = 1,
sub into (1): 2x -3(1) = 5
x = 4

4.{6x+5y=11 -----------(1)
5x-2y=3--------------(2)
2 x (1) + 5 x (2):37x = 37
x = 1
sub into (1): 6(1) + 5y = 11
y = 1
5.{4x-5y=6 --------(1)
24x-9y=1 --------(2)
(1) x 6 - (2): -21y = 35
y = -5/3
sub into (1): 4x-5(-5/3) = 6
x = -7/12