solution to #25 and #29

25.
a function is odd if f(-x) = -f(x).
g(-x)=e^-2x- 1/(e^-2x), which simplifies to 1/(e^2x)-e^2x, which = -g(x). Therefore, the function is odd.

For 29, the graph is of y=0, which makes sense because log(x^4-1)-log(x^2-1)-log(x^2+1) = log((x^4-1)/(x^2-1)/(x^2+1)). (x^4-1)/(x^2-1)=x^2+1, and (x^2+1)/(x^2+1)=1, so the equation is = log(1), which equals 0.

If anyone could explain how to prove #15, that would be great.