Find the first three terms, in ascending powers of xxx, of the binomial expansion of (1−x)−12(1-x)^{-\frac{1}{2}}(1−x)−21
A student substitutes x=1.5x = 1.5x=1.5 into the expansion to find an approximation for 2\sqrt{2}2. Explain the mistake in the student's approach.
By substituting x=19x = \frac{1}{9}x=91 into your expansion, find an approximation for 2\sqrt{2}2. Give your answer to three significant figures.
Practise Edexcel A Level Maths 4.2 Expanding (a + bx)^n with exam-style questions for A Level Maths. 99 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.