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Binomial expansion

binomial expansion question.png
I've expanded part (a) correctly, but I've completely forgotten how part (b) works. Any help?
Moving everything over to one side will create a new quadratic, which you can solve as you see fit.

Just make sure that your solutions satisfy the criteria for the expansion to be valid.
Original post by connor.beja

I've expanded part (a) correctly, but I've completely forgotten how part (b) works. Any help?


11+2x=(1+2x)−1/2\dfrac{1}{\sqrt{1+2x}} = (1+2x)^{-1/2}

From your theory, the expansion for (1+x)n(1+x)^{n} if ∣x∣<1|x| < 1 so in your question you should set ∣2x∣<1|2x| < 1.

Spoiler



Just in case you needed the calculation

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