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    • Thread Starter

    How do you do Q2 on JAN 11 OCR CORE 1?


    Repeat answer to repeat question.

    Well I do not know which explanations you have not understood. However since it is an identity (true for all x).
    Substitute in x=0 to get 5p=2q and also some other value of x to get another equation.

    If you factorise both sides fully you find a common factor of (x+2) on both sides which cancels to give (x-p)(2x+5)=(x-2)(2x+q) which makes life easier.
    Once you sub in x=2, the RHS is zero and the LHS is fairly easy.

    Next use x=-5/2 which makes the LHS zero and the RHS fairly easy

    The key point is knowing what an identity is. You can put in any value of x you like and choosing a sensible value will give you a relatively straightforward thing to do.

    The markl scheme expects you to expand both sides and compare coefficents, this gets you a pair of simultaneous equations in p & q leading to p=2 and q=5. If you need some help on the algebra for this then come back.
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