Originally Posted by

**bobchiba** I posted a problem I had with graphing a quadratic equation but im now not sure if im even using the right formular,

the original expression to graph is P = 85X - X^2 - 550

Am I right in changing this to F(x) = -X^2 + 85X -550?

i.e. a=-1, b=85, c=-550

and then I don't now whether to use either

-b/2a, or, -b sqrt(b^2-4ac)/2a

...in order to get the X vertex.

sorry to post the same sort of question but I'm having real trouble getting through this one with such large values for b and c