Question

Completeing the square x^2+6x=7

Answer 1

Dont know how to work it out at all. need help step by step please!

Answer 2

u want to factor it right

Answer 3

I dont know all i know is i am suppose to complete the square root.

Answer 4

k w8

Answer 5

Thanks

Answer 6

saifoo help him

Answer 7

i don't know how to teach this one

Answer 8

Blahh haah thanks me either. I wanst there for this so im trying to do it on my own no notes or anything !

Answer 9

simply use the quadratic formula.

Answer 10

Thats all ?

Answer 11

Yes! =D

Answer 12

that is less confusing.

Answer 13

Do you move the 7 over and make it -7?

Answer 14

I got -6 +-Square root symbol 64/ 2

Answer 15

\[x^2+6x=7\]
they are asking you solve for x by completing the square
\[x^2+6x+(\frac{6}{2})^2=7+(\frac{6}{2})^2\]
\[(x+\frac{6}{2})^2=7+\frac{36}{4}\]
\[(x+3)^2=\frac{28+36}{4}\]
\[(x+3)^2=\frac{64}{4}\]
now we are trying to get x by itself
so we need to undo the square by square rooting both sides
\[\sqrt{(x+3)^2}=\sqrt{\frac{64}{4}}\]
but remember
\[\sqrt{(x+3)^2}=|x+3|\]
this gives two solutions
\[x+3=\pm \sqrt{\frac{64}{4}}\]
now subtract 3 on both sides
\[x=-3 \pm \sqrt{\frac{64}{4}}=-3 \pm \frac{\sqrt{64}}{\sqrt{4}}=-3 \pm \frac{8}{2}=-3\pm 4\]

Answer 16

-3+4=1
-3-4=-7

Answer 17

Well never mind. Myininaya beat me too it. :)

Answer 18

Thanka anyways. so uhmm what is that -3+4=1 and -3-4=_7?

Answer 19

thanks myininaya i had for got the second step.........i had seen this after along time u brushed off all the rust from my mind........thanks a ton!!

Answer 20

lol you're welcome
i honestly don't understand what you mean what is -3+4=1 and -3-4=-7

Answer 21

Where did that come from why did you put that down?

Answer 22

i didn't have to
i could have left the simplification to you

Answer 23

so you don't understand how to get this
\[-3\pm 4 \]
or you don't know why
-3+4=1
and why -3-4=-7?

Answer 24

oh never mind i know what you did now i was confused on where you got the 3+4 and 3-4 but i see where you got it now

Answer 25

you got it from the simplifyed answer sorry i had a moment

Answer 26

lol you know \[-3 \pm 4 => -3+4 or -3-4\]

Answer 27

Yeah ahah sorry i totally forgot that that is what you do.

Answer 28

this is two expressions written as one

Answer 29

Yeah gottcah. (: thanks you helped ALOTTT! Thanks soo much

Answer 30

you could hav written it as ax^2+bx+c=0
and use the quadratic formula
\[x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}=> x=\frac{-b -\sqrt{b^2-4ac}}{2a} \text{ or } x=\frac{-b + \sqrt{b^2-4ac}}{2a}\]

Answer 31

but as i pointed out earlier it does say solve for completing the square
i mainly just wanted to show you that the quadratic formula is an equation that provides two solutions

Answer 32

Yeah thats whta i am doing and using the formula .