Expand (3+kx)12\displaystyle (3+kx)^{\frac{1}{2}}(3+kx)21, where k k\,k is a positive constant, in ascending powers of x x\,x up to and including x3x^3x3, giving your answer in terms of kkk.
Write down the range of values of x x\,x for which the expansion is valid.
Use your expansion, with k=2k=2k=2 and x=0.1x=0.1x=0.1, to find an approximation of the value of 5\sqrt{5}5. Give your answer to 3 decimal places.
408 exam-style questions on Edexcel A Level Maths Binomial Expansion, covering 4.1 Expanding (1 + x)^n, 4.2 Expanding (a + bx)^n, and 4.3 Using Partial Fractions. Each one has a worked solution and a mark scheme showing where the marks go.