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C4 Binomial expansion. watch

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    \frac{1+x}{1-2x} can be expressed in the form 1+ax+bx^2. Find a and b (6 marks)

    I have no idea where to start. I though to turn it into index form then expand brackets, but you just get a quadratic. Any ideas?
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    Anyone? Sorry this is rather urgent :blush:
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    \dfrac{1+x}{1-2x} = (1+x)(1-2x)^{-1}

    Then expand the second bracket up to x2, so you get:
    = (1+x)(1 + 2x + 4x^2)

    and multiply through :jiggy:

    max is always here
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    (Original post by maxfire)
    \dfrac{1+x}{1-2x} = (1+x)(1-2x)^{-1}

    Then expand the second bracket up to x2, so you get:
    = (1+x)(1 + 2x + 4x^2)

    and multiply through :jiggy:

    max is always here
    Thank you :lovehug:
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    (Original post by Loz17)
    Thank you :lovehug:
    Welcome.
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    How did you get that +4x^2 term though?
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    coz 2x^2 is 4x^2
 
 
 
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