Let \begin{aligned} f(x) &= 8 x+9 x^3 - 8 \\ g(x) &= -2 x^4 + 6 x^3 - 7 \\ h(x) &= 9 x^2 + 8 x^4 - 5 \\ k(x) &= 5 x^3 - 7 x^4 - 8 x^2 \end{aligned} Add or subtract the polynomials as indicated. Simplify your answers completely, and be sure to use a lowercase "x".

(a)

(b)

(c)

(d)