Pretty easy when its only a function of the form $y = ax + b$, however I'm trying to find if this function:
$f(x,y) = 2x + y$
is onto and one-to-one. Is there a procedure to follow to check this? Thanks!
EDIT: My reasoning.
onto:
$z = 2x + y$
$x = (z-y)/ 2$
$y = z - 2x$
Seeing as both $x$ and $y$ can be represented in "safe" ways (no dividing by zero), I'm assuming that the function is onto.
One-to-One:
$2x_1 + y_1 = 2x_2 + y_2$
$2(x_1-x_2) = (y_2-y_1)$
Therefore if $y_2 = y_1$, $x_2 = x_1$.
I guess my reasoning is wrong :/