GCSE maths help please (embarassed face)

[princessparty]

DS1 was doing some maths revison last night and asked me for help with a question.I should really have been able to help DS1 with this , but it's 27 years since I studied maths!
The question was to solve a quadratic equation expressing the answer in surd form
so question was x2+2x-10=0
Thinking about it again this morning

could you do it by
1 completing the square
2 square rooting both sides
3 rearranging to get x on it's own

many thanks to anyone who can help!

[AstronomyDomine]

not sure what surd form is, but my first response to such algebraic questions is option 3 - get x on its own.

[mnistooaddictive]

You need to use the quadratic formula. For the quadratic ax^2+bx+c=0 you do

x=(-b±√(b^2-4ac))/2a
so for the one above you would do
x= (-2±√(2^2-4x1x-10))/2x1
= (-2±√(4+40)/2
= (-2±√44)/2
=(-2+√44)/2 or (-2-√44)/2
It can be simplied further but that is sufficient at GCSE. BTW this is equivalent to completing the square but quadratic formula is on formula sheet so easier

[mnistooaddictive]

AAAgghh
formatting hasnt worked
√ should be + or - square root of

will retry later!

[princessparty]

Thanks very much for your help

We came to x= -1+/-sq root of 11
Is that the same thing? I think it is?
using the formula does seem to be easier but for some reason they've told the kids it's better to 'complete the square' if they can.No idea why!!!

[mnistooaddictive]

yes it is you divide by 2. root 44 is root(4 x 11) which is 2 x root 11
I have no idea who you would complete the square - too much potential for mistakes!

[FreudianSlippery]

OMG! You again!!!
F off there's a dear.