1. Log (x+2) + log (x+4) = log 15 2. 2log 2x + 2log x = 2log 6

log a + log b = log (a×b)

1) log (x + 2) + log (x + 4) = log 15
log (x + 2) (x + 4) = log 15
(x + 2) (x + 4) = 15
x² + 6x + 8 = 15
x² + 6x - 7 = 0
(x + 7) (x - 1) = 0
x = -7 atau x = 1

2) ²log 2x + ²logx = ²log 6
² log (2x × x) = ²log 6
2x² = 6
x² = 6/2
x² = 3
x = ± √3
x = √3 atau x = -√3