This is the problem as I received it, I hope that someone can explain how to do it, as I am at a loss

Correlation Coefficient Definition*

r=(∑((x_{i}-x̄)/Sx))∗((y_{i}-ȳ)/Sy))/n-1

Computational Formula for r**

r=((n∑x_{i}y_{i}-(∑x_{i})(∑y_{i}))/(√(n∑x_{i}^{2}-(∑x_{i})^{2})∗(√(n∑y_{i}^{2}-(∑y_{i})^{2}))

1) How do you get from Definition to Computational? Show that * is the same as **

2)* and ** are for samples, show that you get ** for population correlations coefficient.

I would really appreciate any help on this as I am truly lost on how to do this. Thanks