# How to reduce polynomial?

I have some 4 polynomials like this. these equation is made by polyfit() from MATLAB tool.

eq1) 3.1734x^3 -5.8952x^2 +3.8194x -0.0377
eq2) 2.1489x^3 -3.9026x^2 +2.8169x -0.0160
eq3) 1.0796x^3 -1.9013x^2 +1.8500x +0.0008
eq4) x


then I want to make these 4 polynomials to one polynomial But I don't know how to apply this concept to my 4 polynomials .

# Update :

Here is referencing.

Actually, I want to apply above concepts to in my case.

How can I get a (H^T H)^−1 H^Ty from above equations?