Cramer's Rule 2x2

Problem

Solve the 2x2 linear system A*x = b using Cramer's rule.

x = det(Ax) / det(A) and y = det(Ay) / det(A), where Ax replaces column 0 of A with b and Ay replaces column 1. Return [x, y] as floats, or None if det(A) == 0.

Hint

Compute the three 2x2 determinants with the cross formula.

Test cases

case 1

in: [[[2,1],[1,3]],[5,10]]

expected: [1,3]

case 2

in: [[[1,2],[3,4]],[5,11]]

expected: [1,2]

case 3

in: [[[1,2],[2,4]],[3,6]]

expected: null

case 4

in: [[[3,0],[0,2]],[6,4]]

expected: [2,2]

Starter codePython

def cramer_2x2(A, b):
    # Your code here
    pass

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