f(2)=f(4)=0, f(3)=−2.

Question

f(x)=?

Answer 1

Assuming f is quadratic, start with

y = (x-2)(x-4)
y(3) = -1

So, multiply it by 2 and you have

y = 2(x-2)(x-4) = 2(x-3)^2 - 2