SOLUTION: What number goes under the radical when solving this equation with the quadratic formula? 2x^2 - 4x - 30 = 0

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Question 1204368: What number goes under the radical when solving this equation with the quadratic formula?
2x^2 - 4x - 30 = 0
Found 3 solutions by mananth, josgarithmetic, ikleyn:
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
2x^2 - 4x - 30 = 0
comparing with ax^2+bx+c
a=2 , b=-4,c=-30
b^2-4ac is the discriminant
Plug a b c
(-4)^2-(4)(2)(-30)
16+240= 256
sqrt%28256%29

Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
ax%5E2%2Bbx%2Bc=0
general_solution x=%28-b%2B-+sqrt%28b%5E2-4ac%29%29%2F%282a%29
Your question is asking for b%5E2-4ac expression.

Your specific example is %28-4%29%5E2-4%2A2%28-30%29 and you may compute this.
(The discriminant)

Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
.

On solving quadratic equations using the quadratic formula,  see the lessons
    - Introduction into Quadratic Equations
    - PROOF of quadratic formula by completing the square
in this site.