How many different rows can the array have if the multiple is 4

What is f(3) for the quadratic function f(x)= 2x^2+ + x - 12

Consider the set of all four-digit positive integers less than 2000 whose digits have a sum of 24. what is the median of this set of integers?

Let f(x) = 5/x and g(x)=2x2+5x. what two numbers are not in the domain of f o g