# I learnt something new today!

Calculus Level 4

$\large \displaystyle \int^{4}_{0}\dfrac{x^3}{\sqrt{16-x^2}} \, dx$

If the value of above expression is in the form $$\dfrac{a}{b}$$ where $$a$$ and $$b$$ are coprime positive integers, find $$a+b$$.

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