# Math Help - Determinant >_<

1. ## Determinant >_<

If $f:\mathbb{R}^2\mapsto\mathbb{R}^2\text{ where } f((x_1,x_2))=(x_1+2x_2,2x_1+x_2)\forall x_1,x_2\in\mathbb{R},\text{ then find } f^{-1}$

2. The inverse of a 2x2 matrix can't be hard, can it? What am I missing?

$f^{-1}(u,v)\;=\;\frac{1}{3}(-u+2v,2u-v)$