Show that the transformation T defined by T(x1,x2)... 
Show that the transformation $T$ defined by $T(x_1, x_2) = (2|x_2|, 3x_1 - x_2)$ is not linear.

How can I do this? I know that if
$T(cu + dv) = cT(u) + dT(v) \implies $ $T$ is a linear transformation. I'm not sure how to actually apply this formula.

Hint: If $T$ is linear, then $T(x)=-T(x)$.
