Calculus
# Integration Techniques

If $f(x)=\int \frac{4x}{x^2-2x-3} dx$ and $f(0)=15 \ln 3,$ what is the value of $f(2)?$

If $a$ is a nonzero real number, what is $\int \frac{35}{x^2 - a^2} dx?$

**Details and assumptions**

Use $C$ as the constant of integration.