How to find the $f(3)=y$ with given points? If an quadratic equation $f(x)$ has max value $4$ when $x = 0$ and $f(-2)=0$, what is the value of $f(3) =$ ?

making the ansatz $$f(x)=ax^2+c$$ we get easily $$c=4$$ from $$f(-2)=0$$ we get $$a=-1$$ and our searched function is $$f(x)=-x^2+4$$
