Question

Solve for x: x^2 + 24x + 90 = 0

Answer 1

Use the quadratic formula.

Answer 2

I don't understand the quadratic formula, the lessons aren't very helpful.

Answer 3

Use,
\[x = \frac{-b \pm \sqrt{b^2-4ac }}{2a}\]

Answer 4

The value of
a = 1
b = 24
c = 90/

Answer 5

INsert the values in their places to get the final numerical values.

Answer 6

To see an example, watch this slightly goofy guy:
http://www.youtube.com/watch?v=s80J2dAUUyI

Answer 7

Oh okay hold on..

Answer 8

a is the coefficient of the x^2 value. b is the coefficient of the x value. c is the constant.

Answer 9

I got a strange answer. I don't know if it's right.

Answer 10

the answer will be "strange" in as much as it's not an integer.

Answer 11

Well i got \[-72 \pm \sqrt{3}\] Is that right or no?..

Answer 12

No, that can't be right because the -72 just has nothing to do
with -b/2 where b = 24. And in fact it isn't right. Calculate it again.

Answer 13

No because the original equation i received was \[-12 \pm \sqrt{108}\]

Answer 14

Still no. First, what is
b^2 - 4ac
for
a = 1
b = 24
c = 90

Answer 15

24^2 - 4(1)(90)

Answer 16

\[b^2 - 4ac = 24^2 - 4(90) = 216 \]

Answer 17

Oh I divided before i subtracted.

Answer 18

So what's your answer now?

Answer 19

\[-12 \pm \sqrt{18}\]

Answer 20

the -12 is right. the sqrt(18) isn't

Answer 21

Okay so then i'm not getting this.

Answer 22

\[ \frac{\sqrt{b^2 - 4ac}{2a} = \frac{\sqrt{216}}{2} = \sqrt{216/4} = \sqrt{54} = 3\sqrt{6} \]

Answer 23

hmm ... look like eqn editor is broken.

Answer 24

Haha yeah..

Answer 25

sqrt(b^2 - 4ac)/2a = sqrt(216)/2 = sqrt(216/4) = sqrt(54)
= 3 sqrt(6)

Answer 26

Why sqrt(216/4) ??

Answer 27

because (1/x)sqrt(y) = sqrt(y/x^2)

Answer 28

Oh okay so then the answer is 3 plus or negative √6 ?..

Answer 29

No. I hate giving the answer, but I'm going to give it and ask you to make sure you can get it as well:

\[-12 \pm 3 \sqrt{6}\]

Answer 30

Ohh! So i was right but it just needed to be simplified from √18 to 3√6?

Answer 31

\[\sqrt{18} \ne 3\sqrt{6}\]

Answer 32

so you were not right.

Answer 33

Okay never mind then.

Answer 34

just use your damn scientific calculator.

Answer 35

just use your brain actually because this isn't hard with some practice.

Answer 36

hey jamess

Answer 37

help me