The Marksmith AU

The partial fractions set up wrong

You put a constant over every factor.

A linear factor takes a constant on top; an irreducible quadratic takes a linear numerator — $\frac{Bx+C}{x^2+4}$, never $\frac{A}{x^2+4}$. A repeated factor needs one term per power.

Next time: If the numerator's degree isn't lower, divide first.

Try it: Work one on a block