The function f(x)f(x)f(x) is given by f(x)=1+4xf(x) = \sqrt{1 + 4x}f(x)=1+4x, so that a=4a=4a=4.
Using this value of aaa, write down the quadratic function that approximates f(x)f(x)f(x) when x x\,x is small.
409 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.