Which represents a quadratic function?

f (x) = - 8x3 - 16x2 - 4x

f (x) = x 2 + 2x - 5

f (x) = + 1

f (x) = 0x2 - 9x + 7

A quadratic function is one of the form f (x) = ax^2 + bx + c, where a, b, and c are numbers with a not equal to zero. In the given question, the only function that satisfies the condition of a quadratic function is f (x) = x^2 + 2x - 5 and thus is the correct answer to the question.