Question

can someone please teach me how to "complete the square"

Answer 1

is there a specific example? Its really dividing the coefficient of x or y and then squaring it.
so it the equation was x^2+4x = 0, to complete the square, you would divide 4x by 2 and then square that number.

Answer 2

http://www.youtube.com/watch?v=xGOQYTo9AKY What you are essentially doing is making an equation without perfect square into an equation that has one, which is okay as long as you do everything to both sides of the equation. watch the video, and practice this. It takes time to get good at.

Answer 3

okay so I watched the video I think I got it!
this is the problem 3x^2 - 24x = 27 and I got X=9 and X=-1
is this correct?

Answer 4

Absolutely. Good job!

Answer 5

I'm doing it wrong, I'm trying to solve for 2x^2-20x=8 and I got up until square root of (x+5)^2= plus or minus square root of 21 idk what to do after?

Answer 6

Always be careful about remembering to multiply what you add to the constant side by what you factored out of the original polynomial. In that one you factored out three so had to remember to multiply fifteen by three before adding to the other side. That is where most mistakes happen, but you got it.

Answer 7

2x^2-20x=8
divide each term by 2
x^2 - 10x = 4
(x - 5)^2 = 4 + 25
(x - 5)^2 = 29
take square root on both sides:
x - 5 = +/-sqrt(29)
x = 5 +/- sqrt(29)

Answer 8

I get x = 5 +/_ the sqrt of 29

2x^2-20x = 8
2(x^2-10x+25) = 8+50
2(x-5)^2 = 58
(x-5)^2 = 29
(x-5) = +/- sqrt (29)
x = 5 +- sqrt (29)

Answer 9

x^2 = 24 - 4x
-24 +4x
x^2+4x-24=0
1/2(4)^2= 4
(x^2+4x+4)-24+4=0
(x+2)^2=20

whats next?

Answer 10

(x+2)^2= -20 ***

Answer 11

x^2+4x-24=0
coefficient of x divided by 2 is: 4/2 = 2
complete the square:
(x+2)^2 - 4 - 24 = 0
(x+2)^2 - 28 = 0
(x+2)^2 = 28
take square root on both sides:
x + 2 = +/- sqrt(28) = +/- sqrt(4*7) = +/- 2sqrt(7)
x = -2 +/- 2sqrt(7)
x = -2 + 2sqrt(7) or x = -2 - 2sqrt(7)

Answer 12

I added wrong, didn't I? see after the fact that I got the equation and it's time to "square root" it I get extremely confused?! But I saw my mistake. thank you

Answer 13

Follow one convention and stick to it.
Some textbooks recommend keeping the constant term on the right hand side.
If you follow that convention, then you have to ADD the square of the term (b/2a) to the right hand side when completing the square,

Answer 14

If you keep the constant term on the left hand side then you need to SUBTRACT the square of the term (b/2a) from the right hand side when completing the square.

Answer 15

For example, complete the square: x^2 + 6x = -7
coefficient of c term is 6. Divide by 2. 6/2 = 3.
This 3 will go inside the square. And 3^2 will be ADDED to the right hand side:
(x+3)^2 = -7 + 9 = 2

If the constant is brought to the left side then:
x^2 + 6x + 7 = 0
(x+3)^2 - 9 + 7 = 0
(x+3)^2 - 2 = 0
(x+3)^2 = 2 (same as before).