Question

Please check:

What is the first step in solving x^2 + 2x + 3 = 0 by completing the square?

A. Subtract 3 from each side of the equation.
B. Add 3 to each side of the equation.
C. Factor the left side.
D. Divide both sides of the equation by 2.

My answer: A

Answer 1

@wolf1728

Answer 2

I'd say you are right it is A

Answer 3

Thank you so much

Answer 4

glad to help :-)

Answer 5

@rose4825
@wolf1728
what after "Subtract 3 from each side of the equation"?

Answer 6

The next step is to divide the equation by the coefficient of x^2 and since it is 1 that doesn't have to be done.

Answer 7

It only asks for the first step @3mar.

Answer 8

If you need to know all the steps of completing the square, try this web page http://www.1728.org/quadr2.htm
read the first half.

Answer 9

So you mean that:
\[x^2 + 2x + 3 = 0\]
\[x^2 + 2x + 3 -3= 0-3\]
\[x^2 + 2x = -3\]
\[\frac{1 }{ 1 } x^2 + \frac{ 2 }{ 1 } x = \frac{ -3 }{ 1 }\]
\[x^2 + 2x = -3\]
then add and subtract \((\frac{ 2 }{ 2 })^2\) to the left-hand side
\[x^2 + 2x +1-1= -3\]
\[(x^2 + 2x +1)-1= -3\]
\[(x+1)^2-1= -3\]


So that is the aim of us,,,right?

Answer 10

x^2 + 2x = -3

x^2 + 2x +1= -3 +1
(x+1)^2 = -2
x + 1 = sqrt(-2)
x = sqrt(-2) -1

Answer 11

But I think:
\[x^2 + 2x +1= -3 +1\\(x+1)^2=-2\\ \sqrt{(x+1)^2}=\sqrt{-2}\\x+1=\pm \sqrt{2}~i\\x=-1\pm \sqrt{2}~i\]

therefore:
\[\Huge {x_1=-1+ \sqrt{2}~i\\or\\x_2=-1- \sqrt{2}~i}\]

that is just in case he wants to solve this equation, not to complete the square!!
agree with me @wolf1728

Answer 12

Let's involve @rose4825 also!

Answer 13

i agree with your solution

Answer 14

Hmm it seems rose is offline

Answer 15

That is good,,,and don't forget that the output of the square root results in two quantities (negative and positive)....

That point always makes a confusion in results!

Answer 16

So, I guess you know about completing the square pretty well.

Answer 17

yes. Praise for Allah!
and all of us learn and add new experience every day...that what makes us grow..

Answer 18

I guess so. This place (openstudy) is good for keeping the mind sharp.

Answer 19

I agree with you...but firstly it needs to be controlled and moderated by some serious and honest stuff...

Answer 20

I always thought that this place was fairly well-moderated

Answer 21

Thank you both. I did log off because I had to go to bed, but I understand what you guys mean.

Answer 22

I am happy to hear that.
What matters is that you got the idea!