Find the first four terms, in ascending powers of xxx, of the binomial expansion of (3−13x)5\left(3 - \frac{1}{3}x\right)^5(3−31x)5
Given that xxx is small, so terms in x4x^4x4 and higher powers of xxx may be ignored, show (3−13x)5+(3+13x)5=a+bx2\left(3 - \frac{1}{3}x\right)^5 + \left(3 + \frac{1}{3}x\right)^5 = a + bx^2(3−31x)5+(3+31x)5=a+bx2 where aaa and bbb are constants to be found.
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.