In algebra 1, we spend a lot of time working with quadratic equations. Among other things, we want to know how many roots (solutions) an equation has and whether the roots are real or imaginary numbers.
One way to visualize this is by asking:
- “Which values of x will make the equation equal to zero — that is, will make the graph cross the x-axis?”
I wish my algebra teacher had explained it like James Tanton does. It makes so much sense!
Denise Gaskins' Let's Play Math 
I saw this video some time ago, loved it, but forgot all about it, so thank you for reminding me as this is perfect timing — we’re coming up on the quadratic equation! A picture is worth a thousand formulas!