For the expansion of (1+4x)12\displaystyle (1 + 4x)^{\frac{1}{2}}(1+4x)21, write down the range of values of x x\,x for which the expansion is valid.
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.