Find all 2 × 2 matrices a such that det a−1 and a = a-1

Step-by-step explanation:

Let A be a two x two matrix

A = a b

     c   d

|, if A is its own inverse

Or ad-bc = ±1

ad-bc =1  gives a=d and b = =b and c=-c

If ad-bc =-1 then a=-d, d=-a

Hence the matrices would be of the form

or

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.