Quadratic Formula / Discriminent and roots

[Jessi]

Hello!

I have been absent from school for a couple of days this week, so I've fallen behind on this lesson. I'm doing my make-up work and was hoping that someone here could help me with the last few problems that I seem to have some trouble with.

11) 3x^2 + 2x - 1 = 0 (must use quadratic formula)

-2 +/- sq. root of 2^2 - 4(3)(-1)
-2 +/- sq. root of 16

-2 +/- 4

2, -6 / 6 =

Answer (?): (1/3, -1)

Is that the correct answer?

12) x^2 - 30 = 0 (quadratic formula)

Answer (?): 0 +/- 11 sq. root of 2

18) 2x^2 - 3x = -2 (discriminent)

I don't know how to do discriminents...could someone please explain that problem to me from step one?

Thanks so much in advance for any and all of your help!

 

[Denis]

3x^2 + 2x - 1 = 0 (must use quadratic formula)
-2 +/- sq. root of 2^2 - 4(3)(-1)
-2 +/- sq. root of 16
-2 +/- 4
2, -6 / 6 =
Answer (1/3, -1)
Is that the correct answer?

Yes; good job; BUT try and be clearer; a bit like this:

x = [-2 +- sqrt(2^2 - 4(3)(-1)] / [2(3)]
x = [-2 +- sqrt(16)] / 6
x = (-2 +- 4) / 6
x = (-2 + 4) / 6 or x = (-2 - 4) / 6
x = 2/6 or x = -6/6
x = 1/3 or x = -1

Get my drift?