indices

1)9(3x+1) = 272x
9(3x+1) = (33)2x
9(3x+1) = 36x
9 = 36x / 3x+1
36x-(x+1) = 9
36x-x-1 = 9
35x-1 = 9
35x-1 = 32
∴5x﹣1 = 2
5x = 3
x = 3/5

2)我諗你打錯題目，應該是：
http://hk.knowledge.yahoo.com/question/question?qid=7007100300036
4x+1 + 4x ﹣4x-1 = 19
(4x)(4) + 4x﹣(4x)(4-1) = 19
(4x)(4) + 4x﹣(4x)(1/4) = 19
(4x)[4 + 1﹣(1/4)] = 19
(4x)(19/4) = 19
4x = 19 / (19/4)
4x = 4
∴x = 1

3)6x+2﹣2(6x+1)﹣12(6x) = 2
(6x)(62)﹣2(6x)(61)﹣12(6x) = 2
36(6x)﹣12(6x)﹣12(6x) = 2
(6x)(36﹣12﹣12) = 2
(6x)(12) = 2
6x = 2/12
6x = 1/6
6x = 6-1
∴x = -1