Express the given quantity as a single logarithm. ln(a+b) + ln(a-b) - 9 ln(c)

Here is what I did:

ln a + ln b + ln a - ln b - 9 ln c

The ln b's cancel.

ln a + ln a - 9 ln c

Then combine to one logarithm.

ln(a^2 - c^9)

The outcome I got was incorrect. I was just wondering if you could point me in the right direction or point out my flaws. Thanks!