Which represents a quadratic function?


f(x) = −8x3 − 16x2 − 4x

f (x) = three-quarters x 2 + 2x − 5

f(x) = StartFraction 4 Over x squared EndFraction minus StartFraction 2 Over x EndFraction + 1

f(x) = 0x2 − 9x + 7