least squared problem and linear algebra

I´m presented with with the following problem:

$\displaystyle E(a,b) = \sum_{j=1} ^{N} (y_{j} - (ax_{j} + b)^2)$

Is used to calculate the distance between regular line y = ax + b and a set of points. Its called a least squared problem.

I´m tasked with determing $\displaystyle \frac{\partial E}{\partial a} , \frac{\partial E}{\partial b}$

Next if $\displaystyle \frac{\partial E}{\partial a} = 0 , \frac{\partial E}{\partial b}= 0$

Then this the result in the following set linear system.

More will follow shortly.

Sincerely and Best Regards,

Fred