Question

URGENT.
Steps to derive the quadratic formula.
http://gyazo.com/1a8073a2db1827b75c1430309b55e630

Answer 1

@ganeshie8

Answer 2

So the choices question step 4 thru 7

Answer 3

Lets look at step 4

Answer 4

Do you know how to complete the square?
Did they add the same thing on both sides?

Answer 5

@superdude123 Look through each step carefully.

What are they changing between those two steps? Is that a legitimate operation, yes or no? If yes, then go on to the next one. If not or you're unsure, ask us and we'll help you.

Answer 6

@Kainui I'm thinking it could be step 4.

Answer 7

what seems to be wrong with step 4?

Answer 8

@Kainui Looking at replications of the quadratic formula, step 4 seems to be off.

Answer 9

no it's supposed to be a square ... to make the left side a perfect square for the next step

Answer 10

@PaxPolaris I think it is step 4!

Answer 11

it's not ....

adding \((b/2a)^2\) is necessary to make left side of the equation a perfect square

Answer 12

Yeah how does it seem to be off? A hunch isn't really good enough here @superdude123

Answer 13

Hm, how about step 7?

Answer 14

I think that could potentially be it

Answer 15

then in step 5 ... the right side stays the same , and the left rewritten correctly.

Answer 16

But b/4a was never written.

Answer 17

then in step 6 ... we are taking the square root of both sides ...

Answer 18

but wait a minute it say c/a instead of -c/a ... unlike all other steps

Answer 19

that's your mistake

Answer 20

@PaxPolaris Ohh.

Answer 21

@PaxPolaris I don't know how that slipped. :P

Thanks :)

Answer 22

also there should be a \(\pm\) sign just outside the square root in this step as well

Answer 23

@PaxPolaris Also, could you help with one more thing? I'm not sure how to rewrite my answer.

Answer 24

http://gyazo.com/fec99a2f9a5329d2584b28297eb0ccd5
is the question.

Answer 25

http://gyazo.com/2ce6f6f710ec20fbaa2be7eec370dcff
is my answer.

Answer 26

your answer if \[\pm \sqrt2 \sqrt{-2p-25}\]

is fine ... there are two solutions but we only care about the positive one

Answer 27

\[8p=-2X^2-100\]

isolate the X term

Answer 28

\[8p+100=-2X^2\]

Answer 29

move -2 to the other side

Answer 30

\[{8p +100\over-2}=X^2\]

Answer 31

then take sqrt

\[X= \pm \sqrt{8p+100\over-2}\]

this doesn't match the answer ... but we can move the negative sign from the denominator to numerator

Answer 32

\[X=\pm \sqrt {-8p-100 \over 2}\]

that's the 3rd choice