Jawabanmu

2014-01-31T14:26:57+07:00
3 pangkat 2 x -1 = 81 pangkat 2 x -4
9x - 1 = 6561x - 4
9x + 6561x = -4 + 1
6570x = -3
x = -4,5
bukan kaya gitu, tapi ini soal eksponen
2014-01-31T14:37:14+07:00
3^2x-1 = 81^2x-4
3^2x-1 = (3^4)2x-4
3^2x-1 = 3^8x-16
2x-1 = 8x-16
-1+16 = 8x-2x
15 = 6x
x = 2,5
1 1 1