(a)[2]
Express $5y^2 - 30y + 50$ in the form $5(y + a)^2 + b$, with $a$ and $b$ as constants.
(b)[3]
The function $f$ is given by $f(x) = x^5 - 10x^3 + 50x$ for $x \in \mathbb{R}$. Determine whether $f$ is increasing, decreasing, or neither.
Mathematics 9709 · AS & A Level · Differentiation