The function f f\,f is given by
f(x)=1+axf(x) = \sqrt{1 + ax}f(x)=1+ax
where a a\,a is a non-zero constant.
In the binomial expansion of f(x)f(x)f(x), the coefficients of x x\,x and x2 x^2\,x2 are equal.
Find the value of aaa.
Using this value of aaa, state, using set notation, the values of x x\,x for which the binomial expansion is valid.
Using this value of aaa, write down the quadratic function that approximates f(x)f(x)f(x) when x x\,x is small.
144 exam-style questions on AQA A Level Maths 1.7.1 Binomial expansion. Each one has a worked solution and a mark scheme showing where the marks go.