Question

what's a quadratic function and how do I know if it has two real zeros?

Answer 1

http://www.biology.arizona.edu/biomath/tutorials/quadratic/roots.html

Answer 2

A quadratic function is one of the form f(x) = ax2 + bx + c, where a, b, and c are numbers with a not equal to zero. The graph of a quadratic function is a curve called a parabola. Parabolas may open upward or downward and vary in "width" or "steepness", but they all have the same basic "U" shape.