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# Maths C1 Equation watch

1. Can someone help solve this equation?

10 - x = ()x + 9

= 10 minus x equals (square root of 2) times by x plus 9.

Thanks,

QUESTION SOLVED
2. i get the answer to be ; $x = \sqrt{2}/2$.

Do you have an answer yourself?
3. You need to rearrange the equation so that you have only a multiple of x on one side and a number on the other. Try subtracting 9 from each side of the equation to start with; can you see what the next step would be?
4. I got x=1/(sqrt2 -1)
5. Take the 9 to one side and the x to the other.

Factorise in x.

Make x the subject.

It can probably be rationalised further.

Just have a play around.
6. Thanks got it now

( 1 / {sqrt 2 -1} )

Was failing at the factorise x stage.
7. Could you not get rid of the " square root of 2" by squaring it (giving you 2) and then squaring the rest of the eqn, before solving it?
8. (Original post by Thrug)
Thanks got it now

( 1 / {sqrt 2 -1} )

Was failing at the factorise x stage.
you can still take this further by rationalising the denominator which you would be expected to do. I think you should get my previous answer.... $x = \sqrt{2}/2$
9. (Original post by ScottishShortiex)
Could you not get rid of the " square root of 2" by squaring it (giving you 2) and then squaring the rest of the eqn, before solving it?
i dont think you could because you would also have to sqaure the 'x' in turn which would not be solving the equation...
10. (Original post by hdiriaur)
you can still take this further by rationalising the denominator which you would be expected to do. I think you should get my previous answer.... $x = \sqrt{2}/2$
That's not what you get when you rationalise the denominator, although I agree that rationalising the denominator would be a good thing to do.
11. By rationalising the denominator I got
12. (Original post by Thrug)
Thanks got it now

( 1 / {sqrt 2 -1} )

Was failing at the factorise x stage.
It should be 1/(SQRT[2]+1), which simplifies to SQRT[2]-1 (as you've now found).

Try substituting that into the original equation to test it.
13. (Original post by nuodai)
That's not what you get when you rationalise the denominator, although I agree that rationalising the denominator would be a good thing to do.
oops, thanks for pointing that out! erm in which case would it be, $x = \sqrt{2} - 1$ ?
14. (Original post by hdiriaur)
oops, thanks for pointing that out! erm in which case would it be, $x = \sqrt{2} - 1$ ?
Yup.

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