# How do you factor 121xy + 11zx?

$11 x \left(11 y + z\right)$.
$\therefore$ The Exp. $= 11 \cdot 11 x y + 11 z x = 11 y \cdot 11 x + z \cdot 11 x = \left(11 y + z\right) \left(11 x\right) = 11 x \left(11 y + z\right)$.