Question

Solve the quadratic equation by completing the square.
x^2-12x+7=0

Answer 1

add 29 to both sides.

Answer 2

can you add 29 to both sides?

Answer 3

which sides?

Answer 4

Both.
\[x^2-12+7+29=0+29\]

Answer 5

and why 29?

Answer 6

To make the left side into perfect square because you have to have (-6) (-6) which equals 36.

Answer 7

x^2 - 12x + 7 = 0
x^2 - 12x = -7
x^2 - 12x + (-12/2)^2 = (-12/2)^2 - 7
x^2 - 12x + 36 = 36 - 7
(x - 6)^2 = 29

Take square root of both sides to finish solving for x

Answer 8

Oh. Okay. I still don't quite get it, but lets move on. What shall I do next? :D

Answer 9

Uhh... which one is right?

Answer 10

x^2-2*x*6+7=0
x^2-2*x*6+36-36+7=0
(x^2-2*x*6+36)-29=0
(x-6)^2-29=0
(x-6)^2=29
x-6=29^1/2
x=(29)^1/2+6

Answer 11

Are all of these right, just in different ways?

Answer 12

You add 36 to both sides, not 29

Answer 13

But 36 - 7 = 29

Answer 14

@Hero, no you add 29, because that makes the left side into perfect square.

@Emily778, I know what you are confused about, lets learn how to complete the square.

Answer 15

I'll just do this
x^2 - 12x + 7 = 0
x^2 - 12x = -7
x^2 - 12x + (-12/2)^2 = (-12/2)^2 - 7
x^2 - 12x + 36 = 36 - 7
(x - 6)^2 = 29

Answer 16

@SolomanZelman, if that's true, then explain how I got my result

Answer 17

actually in (a+b)^2=a^2+b^2+2ab
here 2ab is 12x=2*x*6
so u need to make b^2 that is 36

Answer 18

I know exactly how the process works and what to add to both sides.

Answer 19

@Emily778, do you get how I came up with 29? lets do a different example.

GUYS PLEASE, LETS TEACH HER, NOT DO HER WORK>

She needs to understand.

Answer 20

@hero
if u will add 29 both side than
on x^2-12x+7+29=29
x^2-12x+36=29

Answer 21

She'll only understand if those teaching know what they are talking about

Answer 22

STOP ARGUING!

Answer 23

YES, add 29

Answer 24

@hero plzz plzzzz plzzzz for god sake use little of ur mind

Answer 25

@Emily778, do you get how I came up with 29? Do you want to learn how to complete the square?

Answer 26

I think @Emily778 already has it figured out lol

Answer 27

MODERATOR, please don't ruin the thread, and confuse teh asker, lets teach her!

Answer 28

@Hero
What do I do after this? Or is it already done?
x^2 - 12x + 7 = 0
x^2 - 12x = -7
x^2 - 12x + (-12/2)^2 = (-12/2)^2 - 7
x^2 - 12x + 36 = 36 - 7
(x - 6)^2 = 29

Answer 29

Sorry If I was offensive, @Hero .

Answer 30

Finish solving for x @Emily778

Answer 31

Take the square root of both sides

Answer 32

Can you show me how? I am so confused:(

Answer 33

@Emily778 PLEASE read this CAREFULLY.

Do you know how to come up with the number that you have to add to both sides to ake the left side into a perfect square?

Answer 34

to make the left side...typo