Find $a_j$ give m points as $(x_i,y_i)$ where: $i = 1,2,...,m$, $y=\sum_{j=0}^n a_j x^j \quad n < m$

Question

I have been trying to solve this problem, is this answer right? it's my first time solving a problem in the curve fitting least-squares that has a finite series in it.

find $a_j$ give m points as $(x_i,y_i)$ where: $i = 1,2,...,m$, $y=\sum_{j=0}^n a_j x^j \quad n < m$. (the problem and answer in the picture)

my solution:

if wrong, what approach should I take to solve it?