express the given quantity as a single logarithm: ln(a+b)+ln(a-b)-8ln(c)

Answer 1

ln[(a+b)(a-b)c^8]
= ln[8c(a^2-b^2)]

Answer 2

I overlooked the minus sign.

ln[(a+b)(a-b)/c^8]
= ln[(a^2-b^2)/8c]