Question

Solve. x2 – 8x + 4 = 0

Answer 1

im posting the answers now. :)

Answer 2

\[x^2-8x+4=0\]

You can complete the square or use a quadratic formula. Which one would you prefer?

Answer 3

Do you just need help understanding how to get the answer? Or did you figure it out?

Answer 4

i need help understand how to get the answer @blarghhonk8

Answer 5

@Godgirl, do you want to complete the square or use a quadratic formula to do your problem, or go through each method?

Answer 6

ah I see, okay, so, judging by the answers posted, probably would be simplest to use quadratic formula.

Answer 7

@student_basil Idk will both methods give me the same answer?

Answer 8

Both methods will give you the same answer.

x^2-8x+4=0

completing the square

1) Add 12 to both sides
2) factor the left side
3) square-root both sides
4) do it from there...

Answer 9

\[x = \frac{-b\pm\sqrt(b^2-4ac)}{2a}\]
where the quadratic gives:\[ax^2+bx+c=0\]

Answer 10

ill do the quadratic formula.

Answer 11

a=1
b= 8
c= 4 :)

Answer 12

yep, plugging into the equation then we have \[\frac{-8}{2(1)}\pm\frac{\sqrt(8^2-4*1*4)}{2(1)}\]I split the fraction so that it would better match the given answer choices

Answer 13

@blarghhonk8 ok thanks so much! im gonna try to solve it so jus a sec. :)

Answer 14

\[-8\pm \sqrt{48}\]

Answer 15

over 2 @blarghhonk8

Answer 16

yes. and you can bring the 2 into the radical by squaring it. Not sure how familiar you are with it. But basically it works like this:

Answer 17

\[2*\sqrt(x)=\sqrt(2^2x)=\sqrt(4x)\] Or\[\frac{1}{2}*\sqrt(x)=\sqrt(\frac{x}{4})\]

Answer 18

Understand how I did that?

Answer 19

not one bit @blarghhonk8

Answer 20

haha. Alright, it is a bit weird if you haven't done much with it before. But, you know how if you have say, 2x+2 you can factor out a 2 and get \[2x+2=2(x+1)\]?

Answer 21

Well, it is a similar concept, except, since you are factoring into/out of a square root, you must square/square root (respectively) what you are factoring

Answer 22

@blarghhonk8 lol ive seen it before

Answer 23

Another way you can think of it is like this \[\sqrt(4x)=\sqrt(4)\sqrt(x)=2\sqrt(x)\]

Answer 24

in your case, it is a sqrt divided by a number so \[\sqrt(48)/2=\sqrt(48)/\sqrt(4)=\sqrt(48/4)\]

Answer 25

@blarghhonk8 sooo u do 48 squared divided by 2? or am i wrong.
Srry if im giving u a hard time im like really not that great in this subject

Answer 26

Nope, that would be correct. Leaving it in the sqrt of course. :)

Answer 27

that would be 24^2

Answer 28

@blarghhonk8

Answer 29

oh sorry, no, you do \[\sqrt\frac{48}{4}=\sqrt(12)\]

Answer 30

@blarghhonk8 Oh ok and srry if this is a dumb question but... where did we get the 4.....

Answer 31

It's not really dumb. And that is a bit confusing. But, we got it down to \[\frac{-8}{2}\pm\frac{\sqrt(48)}{2}\]right?

Answer 32

this gives us\[-4\pm\frac{\sqrt(48)}{2}\]

Answer 33

But, \[\frac{1}{2}=\frac{1}{\sqrt(4)}\]right?

Answer 34

so, \[\frac{\sqrt(48)}{2}=\frac{\sqrt(48)}{\sqrt(4)}\]and then since it is a sqrt on top and on bottom, we can just take the sqrt over the whole thing. so the equation becomes\[\frac{\sqrt(48)}{\sqrt(4)}=\sqrt(\frac{48}{4})=\sqrt(12)\]

Answer 35

giving a final answer of \[-4\pm\sqrt(12)\]Were you able to follow that alright?