log3(x + 7) < log9(x2 + 77)
Using the change-of-base formula:
[ log(x + 7) / log(3) ] < [ log(x2 + 77) / log(9) ]
[ log(x + 7) / log(3) ] · log(9) < log(x2 + 77) [multiply both sides by log(9)]
[ log(x + 7) / log(3) ] · log(32) < log(x2 + 77) [change 9 into 32]
[ log(x + 7) / log(3) ] · 2 · log(3) < log(x2 + 77) [use property of logs]
[ log(x + 7) ] · 2 < log(x2 + 77) [cancel the log(3) factors]
2 · log(x + 7) < log(x2 + 77) [rewrite]
log(x + 7)2 < log(x2 + 77) [use property of logs]
(x + 7)2 < x2 + 77 [raisee both sides to power of 10]
x2 + 14x + 49 < x2 + 77 [multiply out]
14x + 49 < 77
14x < 28
x < 2