Question about using the discriminant. (1 Viewer)

[JFX]

What is the discriminant used for and how do you know which types of questions requires the use of the discriminant.

For example, the last question 16c in the 2012 paper requires you to use the discriminant, but i don't understand why. Help would be much appreciated thanks and best of luck for all tomorrow.

 

[andybandy]

the discriminant is used to find whether their a 1 roots, or 2 or no roots and whether their equal, if the discriminant is less then zero, then the parabola doesnt touch the x axis, if its equal to zero, it touches the x axis once, and if its greater than zero it touches it twice. look up some youtube tutorials

 

[JFX]

Ok, but how would you use that to solve 16c of the 2012 paper?

 

[andybandy]

the circle and parabola intersect at tangents, and a tangent to a circle only has one solution, so you have to solve the equation simultaneous and let the discriminant equal 0

 

[JFX]

the circle and parabola intersect at tangents, and a tangent to a circle only has one solution, so you have to solve the equation simultaneous and let the discriminant equal 0

Alright i understand that. The next part, how the heck do you answer that >.>?

 

[andybandy]

now that bit is still mind fucking me -.-

 

[JFX]

now that bit is still mind fucking me -.-

=( well, at least it won't likely appear in tomorrow's paper. Thanks alot anyways =)

 

[andybandy]

all goods

 

[Queenroot]

=( well, at least it won't likely appear in tomorrow's paper. Thanks alot anyways =)

Nek minnit.
I am pretty sure half the state doesn't even attempt that question, so the fact that you're doing it shows how brilliant you are.

 

[JFX]

haha, thanks, just trying to squeeze as much marks out of the paper as possible