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    OCR Jan 2008 Q 9 last part has the answer that k lies outside of the range between root 3 -2 and root 3 + 2.
    It is tempting to write \sqrt 3+2< k < \sqrt 3-2 rather than separately saying
    k>\sqrt 3+2 or  k < \sqrt 3-2.

    In the mark scheme, the former case loses at least one mark. Whilst I agree it is a bit unclear, why is it wrong?

    Is it because the notation implies that k can be in both domains at the same time or is it something else?
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    (Original post by nerak99)
    OCR Jan 2008 Q 9 last part has the answer that k lies outside of the range between root 3 -2 and root 3 + 2.
    It is tempting to write \sqrt 3+2< k < \sqrt 3-2 rather than separately saying
    k>\sqrt 3+2 or  k < \sqrt 3-2.

    In the mark scheme, the former case loses at least one mark. Whilst I agree it is a bit unclear, why is it wrong?

    Is it because the notation implies that k can be in both domains at the same time or is it something else?
    The first doesn't make any sense. With your explanation I know what you're trying to do but this use of the notation is just wrong. Use the second method.
    The first implies that \sqrt 3 - 2 > \sqrt 3 + 2.
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    Thanks. I just did not look at the wider picture.
 
 
 

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