Question

I know I have to do the quadratic equation to unpack this: but I'm having trouble.
14x^2-10x-4356=0

Answer 1

use this formula

Answer 2

I got 18, I think that is correct. Thanks

Answer 3

Actually you can solve this by factoring which is way easier.

So you can take out a "2" and will get 2(x-18)(7x+121)=0

Solve for x-18=0 and you'll get x=18 as one of the answers.
Solve for 7x+121=0 and you you'll get 7x=-121 and therefore x=-121/7 as your other answer.

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Answer 4

Ok, but how come you can take out a 2, what happens to that 2

Answer 5

You simply do not use it. You only use what you have inside your parenthesis.

Answer 6

Factoring:

\(14x^2-10x-4356=0\)

\(2(7x^2-5x-2178 )=0\)

Divide both sides by 2.

\(7x^2 - 5x - 2178 = 0\)

\(\dfrac{(7x - 126)(7x + 121)}{7} = 0\)

\((x - 18)(7x - 121) =0\)

\(x = 18\) or \(7x = 121\)

\(x = 18 \) or \(x = -\dfrac{121}{7} \)

Quadratic formula:

\(14x^2-10x-4356=0\)

Factor out a 2 and divide both sides by 2 like above.

\(7x^2 - 5x - 2178 = 0\)

\(x = \dfrac{-(-5) \pm \sqrt{(-5)^2 - 4(7)(-2178)}}{2(7)} \)

\(x = \dfrac{5 \pm \sqrt{25 +60984}}{14} \)

\(x = \dfrac{5 \pm \sqrt{61009}}{14} \)

\(x = \dfrac{5 \pm 247}{14} \)

\(x = \dfrac{252}{14}\) or \(x = - \dfrac{242}{14} \)

\(x = 18\) or \(x = -\dfrac{121}{7} \)

Answer 7

Thanks everyone:) It helped a lot.