# How do you factor by grouping, r^2-4tw +2wr - 2tr?

Collect $r$ frm the first and third term and $- 2 t$ from the second and fourth:
$r \left(r + 2 w\right) - 2 t \left(2 w + r\right) =$
$= \left(r + 2 w\right) \left(r - 2 t\right)$