yr2 chap 4 binomial expansion

• to expand (1+bx)^n where n is a positive integer, use the top formula in the formula book, that is the easy one
• to expand (1+bx)^n where n is not a positive integer, use the second formula in the formula book
• to expand (a+bx)^n where a is not 1 and n is not a positive integer, rearrange (a+bx)^n into the form (a(1+bx/a))^n which gives you a^n (1+bx/a)^n, you can then use the second formula in the formula book to expand it and remember to multiply everything by a^n afterwards
• the second formula in the formula book is only valid for |x| < 1

  when expanding (ax+b)^n, it is only valid for |a/b| < 1, so for |x| < |a/b|