Quadratic Form Value

Problem

Compute the quadratic form x^T A x for a square matrix A and vector x:

sum over i, j of x[i] * A[i][j] * x[j]

The result is a scalar; A and x may contain negative entries.

Hint

It is equivalent to the dot product of x with A*x.

case 1

in: [[[2,1],[1,3]],[1,2]]

expected: 18

case 2

in: [[[1,0],[0,1]],[3,4]]

expected: 25

case 3

in: [[[0,1],[-1,0]],[1,2]]

expected: 0

case 4

in: [[[2,0],[0,5]],[0,0]]

expected: 0

Starter codePython

def quadratic_form(A, x):
    # Your code here
    pass

4 test cases · run your code against them in the editor