Graphing Horizontal & Vertical Lines Examples

Graph x = -3.

Hmm…there's no y variable in sight, so no matter what value we "plug in" for y, the x-value will always be -3.

This makes it a vertical line passing through the x-axis at x = -3.

Which axis does the graph of y = 4 cross through and at what point?

Poor little x. It wasn't invited to the graphing party. Maybe its invitation got lost in the mail?

There's no x variable at this party, so this graph crosses through the y-axis. But where?

It crosses at y = 4, but we need to name this point. Because our equation slices through the y-axis, the x-value is 0 so the point is (0, 4).

What's the equation of a horizontal line passing though the y-axis at 24?

All horizontal lines look like y = (some number) when we flip 'em into equation mode, so we know we won't have any x's in our equation. What number should we set y equal to? That's the million-dollar question.

Because it crosses the y-axis at 24, it also has the number 24 in it. So the equation is y = 24.

Oh, and we lied about the whole million-dollar thing. Sorry.