Find a positive, continuous function f(x) which satisfies the integral equation

$\displaystyle f(x) = \pi \left( 2 + \int_{1}^{x} 3f(t) dt \right)$

Hint: start by differentiating each side.

I Have Absolutely NO Idea On How To Do This Problem, I Don't Even Understand The Hint.

Thanks To Anyone Who Helps <3

: )