Thursday 17 May 2012

Sequences

Sequences: An ordered list of numbers that follow a certiain pattern (or rule).

Example:

4, 7, 10, 13, 16, 19, 22

Use the following process to help find a formula for the pattern.










n: is the position or place value
tn: value of that position











When looking at the pattern this way, it is easy to see the it just adding three. So the formula would be.

tn= n-1+3


Or










tn=7n-9



Arithmetic Sequences:

(i) Recursive defintion: An order list of numbers generated by continnous adding value (the common)
(ii) Implictit defintin: An oredered list of numbers where each number n the list is generated by a linear equation.

Common Difference (d):
(i) The number that is repeatedly added to successive term in an arithemic sequence.
(ii) Fommr the implicit definitiion, d is the slope of the linear equation. 

Recursivw: add to what you have. Ex: tn= tn-1+3
Explicit: a formula that uses the position or "n" value to find. Ex: tn= 3n+7

You should also know how to find the common difference

        d = tn - t(n - 1)

        d is the common difference

        tn is an arbitrary term in the sequence

        t(n - 1) is the term immediately before tn in the sequence

As well you should know how to find the nth term in an arithmetic sequence
        tn = a + (n - 1)d
        tn is the nth term
        a is the first term
        n is the "rank" of the nth term in the sequence
        d is the common difference