Linear and other Functions

Recall that an expression is only a function if it passes the vertical line test. Test this by graphing each function and looking for one which fails the vertical line test. (The vertical line test consists of drawing a vertical line through the graph of an expression. If the vertical line crosses the graph of the expression more than once, the expression is not a function.)

Functions can only have one y value for every x value. The only choice that reflects this is:

${\displaystyle y=\pm <!--\; \pm \; -->\sqrt{x^2-<!--\; -\; -->7x+5}}$