4k^2-2k-5=0 Please Please Please help me??

- anonymous

4k^2-2k-5=0 Please Please Please help me??

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- reemii

wanna find the solutions i guess?

- Luigi0210

Have you tried synthetic division? c:

- reemii

there's a formula for an equation in the form \(ax^2+bx +c=0\). (with the discriminant)

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## More answers

- Luigi0210

Oh, yea use the discriminant like @reemii says.. this will determine weather or not it will factor

- anonymous

Use the quadratic formula to solve the equation. I think its gonna be a fraction with square roots and stuff.

- Luigi0210

Have you tried it?

- reemii

@kika_rayne yes, that one.

- anonymous

Tried what? Solving it? I dont even know where to start

- anonymous

|dw:1370031673895:dw|

- anonymous

I dont know what to do. omg im going to fail math! Today is my last day to get it to a passing grade and i have to go to work soon!! Thanks fo rtrying everyone

- anonymous

Wait is it 4 - or + 8? so like, -4, 12?

- reemii

oops, link is bad

- reemii

if the Δ=\(b^2-4ac>0\), there will be two solutions given by that formula with the fraction and root and all.
if Δ=0 only one solution (same formula)
if Δ<0 no solutions (no real numbers)
as someone said, here \(a=4,b=-2,c=5\).

- anonymous

what does the triangle mean?

- reemii

it's a symbol (delta) for the value called discriminant. it's usually noted like that.

- anonymous

ok, so what should i do? I really dont care about learning this, i just need to pass and i will study this summer

- reemii

the answer to the question is a 2-step answer.
1) compute this \(\Delta\).
2) find the solutions (using the formula) in case there are.
(that's something you must remember for your exams)
here:
1. \(\Delta=b^2-4ac = (-2)^2 - 4 \times 4 \times (-5) = 4 + 16\times5 = 4+80=84\).

- anonymous

maybe this will help..idk

##### 1 Attachment

- reemii

2. Because \(\Delta>0\), there will be two solutions.
the formula is \(-\frac{-b\pm\sqrt\Delta}{2a}\).
first solution: \(-\frac{-b +\sqrt\Delta}{2a} = -\frac{-(-2) + \sqrt{84}}{2\times 4}\)
second solution: \(-\frac{-b -\sqrt\Delta}{2a} = -\frac{-(-2) - \sqrt{84}}{2\times 4}\)
you could make some simplifications in the fractions but that's not crucial.

- reemii

oops, i made a mistake.
remove all big minus signs in front of the fractions.

- reemii

it should be
first solution: \(\frac{-b +\sqrt\Delta}{2a} = \frac{-(-2) + \sqrt{84}}{2\times 4}\)
second solution: first solution: \(\frac{-b -\sqrt\Delta}{2a} = \frac{-(-2) - \sqrt{84}}{2\times 4}\)

- reemii

(so it's \(\frac{-b\pm\sqrt\Delta}{2a} \) for the general formula.)
To get used to that method do at least 20 exercises, you'll memorize it easily.

- anonymous

-7.2/8 ?

- reemii

oops,
first solution: \(\frac{2+\sqrt{84}}{8}=1.39...\)
second solution: \(\frac{2-\sqrt{84}}{8}=-0.8956...\)

- anonymous

Never mind. If i get wrong enough times, i get a new question. So i dont even have this question anymore because i got it wrong. Thanks @reemii and @physicsboffin @DEVESHkishore and @Luigi0210 anyway

- Luigi0210

I'm sorry
D:

- reemii

ohh -7.2/8 is right! it's one of the two solutions.

- anonymous

The answer was k = 1+[(sqr)21] 1-[(sqr)21]
______________ _____________
4 4

- reemii

yes, your answer is (1-sqrt(21))/4. they just didn't compute the value, instead they made simplifications.

- anonymous

Oh well, They gave me a new question anyways, but thanks for helping

- reemii

11.2/8 is the other answer. you just didn't do it yet?
don't get discouraged, you have found one of the two answers.!

- reemii

solutions*

- reemii

another quadratic equation?

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