$\displaystyle ln(y+1)+ln(y-1)=2x+ln(x)$

So if both sides are exponentiated with base e then the resulting left side of the equation comes out to by my solutions manual:

$\displaystyle (y+1)*(y-1)$

I am wondering by what arithmetic or property that the "+" on the left hand side of the equation turned into a "*" or a multiplication.

The whole equation turns out to be:

$\displaystyle (y+1)*(y-1)=e^(^2^x^)*x$

Thanks for any responses...