In the binomial expansion of (1+bx)n(1 + bx)^n(1+bx)n, where n n\,n is a rational number and b b\,b is a positive constant, the coefficient of x x\,x is 6 and the coefficient of x2 x^2\,x2 is -18.
Show that n=12\displaystyle n = \frac{1}{2}n=21 and find the value of bbb.
State, using set notation, the range of values of x x\,x for which the expansion is valid.
Find the coefficient of x3 x^3\,x3 in the expansion.
36 exam-style questions on CCEA A Level Maths 3.3.7 Sequences and series (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.