Equations don't really have x intercepts, functions or curves do. They're also known as the zeros of the function. When we set a function equal to zero we get an equation to solve, and the zeros of the function become the solutions or roots of the equation.
If a quadratic equation only has one root, that's a repeated root corresponding to a discriminant of zero.
In this example our equation is something like
, or expanded
The discriminant
here is
