**"Use the formal definition of the derivative and the rules for limits to find the derivatives of the functions".**

The formal definition in my book is \(\displaystyle f'(x)=\lim_{\Delta x \rightarrow 0} \frac{f(x + \Delta x) - f(x)}{\Delta x}\)

I have to find the derivative of that guy: \(\displaystyle x^{2} + \frac{3}{x}\)

It seems easy but I just have no idea how to do that, I've tried many times. Could you please help me? I'd like to know how to do that thing. Thank you so much in advance!