Transforming a matrix into a quadratic form

The a2q command finds the quadratic form corresponding to a symmetric matrix.

a2q takes two arguments:
- A, a symmetric matrix of a quadratic form.
- vars, a vector of variable names whose size is the same as the number of rows of A.
a2q(A,vars) returns the symbolic expression for the quadratic form.

a2q([[0,1],[1,0]],[x,y])

2 x y

a2q([[1,2],[2,4]],[x,y])

x²+4 x y+4 y²