Verified answer

ln(a+b) + ln(a-b) - 2lnc

=> ln(a+b) + ln(a-b) - lnc^2

=> ln[(a+b)(a-b)] - lnc^2

=> ln(a^2 - b^2) - lnc^2

=> ln[(a^2 - b^2) / c^2]