how can you tell whether the equation of a parabola will touch the x axis at only one point?

Question

anonymous · Answer

Using the quadratic formula and the discriminant. The discriminant is the B^2-4ac. If it is positive, there is two real solutions. If it is equal to 0, there is one real and one imaginary. If it is negative, there is two imaginary solutions.

anonymous · Answer

is there a way to tell just by looking at the equation?

anonymous · Answer

this can help you http://answers.yahoo.com/question/index?qid=20091116194157AAUb22j

anonymous · Answer

aright. Thanks for the help! You have good karma coming back to you! :)

anonymous · Answer

Jjajajaj yes :D Could you tick best response please :D