Multiple Linear Regression Least Squares Estimator

Show the Proof. In this video I show the math behind deriving the Least Squares Estimator, b, for the Multiple Linear Regression Model

[tvvt]

2:36 wait why is e multiplied by e transpose the same as e^2?

[mohammedalsubaie]

4:26 how they both are equal? could you please explain that, I would really appreciate it.

[ekteshafatdaily]

Why is there no Beta node in the equation (the y intercept)?

[aswathmg]

To find b, you are setting the derivative to 0. Bit confused here. I understand that to get the local minima or maxima, we try to find where the slope is 0. But this would give us both the minima and maxima, right. But here we just need the minima.