L.C.M.

1.12a.
Let a is 1.
a, 4a and 12a=1,4 and 12
So the LCM is 12a.
2.18a.
Let B is 1.
3b, 6b and 9b=3, 6 and 9
So the LCM is 18a.

2008-01-30 20:27:01 補充：
Sorry 2. is 18b not 18a.

我地假設a=1
a=1
4a=4
12a=12
1,4,12的LCM係12
1,2,,3,4,5,6,7,8,9,10,11,12
4,8,12
12
已經知道12a係a同4a同12a的最少公倍數

2.
如b=2
3b=6
6b=12
9b=18
好似頭先
6.12.18.24.30.36
12.24.36
18.36
大家最少公倍數係36

1.a,4a,12a
Let a= 10
10,40,120L.C.M:120
The L.C.M is(120/10)a=12a



2.3b,6b,9b
Let b=10
30,60,90LCM=:180
The L.C.M. is (180/10)b=18b

1.12a
2.9b

1.12a(a x 12，4a x 3，12a x 1)
2.18b(3b x 6，6b x 3，9b x 2)

1.12a
2.18b

1.12a
2.9b