Sequences and series

Sequences are shown as things like a1, a2 a3 a4......an with n being the last term.  An arithmetic sequences is a sequence that is made by adding or subtracting. A geometric sequence is a sequence that is made by multiplying or dividing.  The general equation of an arithmetic sequence is an=a1+(n-1)d and the recursive equation is an+1=an+d where d is the common difference between an+1 and an.  The general equation of a geometric equation is an=a1rn-1 and the recursive equation is an+1=anr where r is the common ration of an+1/an.  Another thing we looked at is series which uses the symbol ∑.  This is used for summation notation and on top of the symbol is n (where you end) to the right of the symbol is the equation and the bottom of the equation is where you start.  To use summation notation you start at the number it tells you to and plug the numbers into the equation until you reach the number at the top.  Here is an example of summation notation.