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# Alevel edexel maths watch

1. Could any one help me on answering this question as I keep doing it and getting +4x cubes instead of 12x cubes
The question- by first writing(1+x)/(1-2x) as (1+x)(1-2x) to the -1 show that the cubic approximate is 1+3x+6xsquared +12x cubed and then state the range of values of x for which the statement is valid.
2. Well, expand (1-2X)^-1 using the binomial theorem and then multiply the terms by (1+X) until you reach ALL terms in X^3, then simplify from there.
3. Ok thankyou

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Updated: October 22, 2017
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