$y\propto x^2$, and $y=45$ when $x=3$. Find $y$ in terms of $x$. Find $y$ when \(x=

Question

$y\propto x^2$, and $y=45$ when $x=3$. Find $y$ in terms of $x$. Find $y$ when $x=5$. Find the positive value of $x$ when $y=320$.

Accepted Answer

(a) $y=5x^2$; (b) $125$; (c) $8$.

Direct and Inverse Proportion