# Can I find the equation of a quadratic function when only two of its points are known?

Think about the quadratic. When we substitute the points, $x$ and $y$ are no longer the variables in the system of linear equations; they become the constants. $a$, $b$, and $c$ now become the variables of the system.
$> y = a {x}^{2} + b x + c$
In general, if we have a degree $n$ polynomial, we require $n + 1$ points to determine the polynomial function.