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    • Thread Starter

    Hi I have been stuck on how to approach this question for ages now and still don't know how to start it or if I am starting it right - I have done heard of questions with a quadratic and linear factor but never a cubic factor - Please help!!

    A polynomial P(x) is the product of (x^3+ax^2-x-2) and x-b.
    (a) The coefficients of x^3 and x in P(x) are zero. Find the values of a and b.

    So far I have re-written P(x) given that the co-efficients of x^3 and x are 0 to be:
    And then I expanded the brackets to equal:
    = -abx^2 + 2b

    But then I am unsure how to use this to solve for a and b and don't know if I have interpreted the question right?
    • Community Assistant

    Community Assistant
    (Original post by Glitterring)
    Well firstly you should rewrite

    P(x)=(x^3+ax^2-x-2)(x-b) = x(x^3+ax^2-x-2)-b (x^3+ax^2-x-2)

    in its expanded form, and then collect the coefficients of x^3 and x which should be in terms of a and/or b. Set them equal to 0.
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Updated: January 28, 2017
“Yanny” or “Laurel”
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