Hich represents a quadratic function? f(x) = 2x3 + 2x2 – 4 f(x) = –7x2 – x + 2 f(x) = –3x + 2 f(x) = 0x2 + 3x – 3

Remember that a quadratic function is a function of the form . The only function that we have of such form is 
where 



Notice that the fourth function  also appears to be a quadratic function, but since any quantity multiplied by zero is zero, ; therefore the function is not quadratic, but linear: .

We can conclude that the quadratic function of our set is f(x) = –7x2 – x + 2

Where are the functions?