What i have done is i have found the factors of the polynomial, 10 & -2.
facing problems finding a and for part i...
Well, you already know that $\displaystyle f(-2)=f(10)=0$ , so substitute this in $\displaystyle f(x)$ and get two linear equations in two variables $\displaystyle a,b$ and...solve!
for part ii, do i have to use long division?