Eigenvalues 2x2

Problem

Compute the real eigenvalues of a 2x2 matrix from the characteristic polynomial

lambda^2 - tr(A)*lambda + det(A) = 0

Return [larger, smaller] as floats, or None if the discriminant tr^2 - 4*det is negative.

Hint

The trace is the sum of the eigenvalues and the determinant is their product.

case 1

in: [[[2,0],[0,3]]]

expected: [3,2]

case 2

in: [[[4,1],[2,3]]]

expected: [5,2]

case 3

in: [[[0,1],[-2,-3]]]

expected: [-1,-2]

case 4

in: [[[1,1],[-1,1]]]

expected: null

Starter codePython

def eigenvalues_2x2(A):
    # Your code here
    pass

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