College algebra
posted by Belle .
Given a quadratic equation in the form y = ax2 +bx +c , and four choices of graphs representing that equation, how can you tell which choices could be eliminated right away by looking at the equation and looking at the graphs and doing some minimal calculations and not actually plotting any of the points? Please be specific and provide an example of an equation.

Wouldn't it be great to see the four choices?

At least, from the sign of a, one can tell whether it is concave upward or downward
a>0 => concave upward.