log8-log4. log8+log4

log8-log4 = log(8/4) = log2

log8+log4 = log(8*4) = log32 = 5log2
Now, if that sly little dot means multiplication, then go on below.
log2*log32
log2 * 5log2
5(log2)^2
or,
(log8)^2 - (log4)^2
(3log2)^2 - (2log2)^2
9(log2)^2 - 4(log2)^2
5(log2)^2