# Is every straight line the graph of a function?

Sep 11, 2014

No, every straight line is not a graph of a function.

Nearly all linear equations are functions because they pass the vertical line test.

$y = 100$
$y = x$
$y = 4 x$
$y = 10 x + 4$
$y = - 2 x - 9$

The exceptions are relations that fail the vertical line test.

x = some constant

$x = 0$
$x = 99$
$x = - 3$