Which of the following quadratics has a minimum?

Answer:
When a quadratic equation's x^2 coefficient is positive, its graph is "U-Shaped" and has a minimum.
Of the equation's listed, the only equation that has a "U-Shaped" graph and would have a minimum is C or 3x^2 +2x -7.
Source: http://www.1728.org/quadr3.htm
Step-by-step explanation: