Solve x^2 + 10x - 11 = 0 by completing the square
Ok, so I need help with this, I have the answer and I know how to do it, I just want to check it.

Question

Solve x^2 + 10x - 11 = 0 by completing the square 
Ok, so I need help with this, I have the answer and I know how to do it, I just want to check it.

campbell_st · Answer

ok... to you need to group a few things 

$$x^2 + 10x = 11$$

to complete the square find half of 10 and  then square it... that's the value that makes the perfect square

then add it to both sides..

anonymous · Answer

Ok that's a bit different then how I learned it but I think it's pretty much the same thing.. 
I would do x^2 + 10x + 25=11+25

Then group it to where it's 
(X+5)^2=36

Then you would put the (x+5)^2 under a radical sign, and the 36 under the radical sign, and you can't forget the plus and minus sign

campbell_st · Answer

that's correct

anonymous · Answer

But I don't know what to do after

campbell_st · Answer

ok... so when you take the square root there are 2 solutions, the positive and negative

so take the square root of both sides

$$x + 5 = \pm \sqrt{36} ~~or~~~x + 5 = \pm 6$$

now subtract 5 from both sides of the equation and you get 

$$x = -5 \pm 6$$

so you ahve 2 equations 

x = -5 -6       and      x = -5 + 6   

does that make sense

anonymous · Answer

Yes, see, I did all that But I had three instead of six. But thank you so much! I'm glad I checked with someone :)