Using logarithms property of log(x)+log(y)=log(xy)
so here, you can sum the equation to;
so you can simply say that;
and by multiplying (x+6)*(x-6)
and as you know also that;
is same as
so you can simply state it as;
And you can check your work by substituting with 10 instead of x in the original function.
Hope this helps!