April Fool's Day.

April 1st

National Doctors' Day

March 30th.

oh no ...

I don't even know what to say.

oh no ....

wow. Who does that

cute baby

lol

Showing posts with label progression. Show all posts
Showing posts with label progression. Show all posts

Geometric Sequences

A geometric sequence, or geometric progression, is a sequence defined by u1 = a and u i+1 = rui, where r is not equal to 0 or 1.
Examples :

   {2, 4, 8, 16, 32} is a geometric term with six terms.
   {2, 1, 0.5, 0.25, 0.125, 0.0625, . . .} is an infinite geometric sequence.


I will skip the proving parts and jump directly to the formula gained from deriving the equations.

The sum of the geometric series a + ar + ar^2 + ... + ar^n-1, with n terms, is





S∞ is called the sum of infinity of the series.


This following examples are the typical exam-typed question. You should try it out.


Ex. Express the recurring decimal 0.296296296 ... as a fraction.

            The decimal can be written as
                        0.296 + 0.296 x 0.001 + 0.296 x (0.001)^2 + ... and so on
            which is a geometric series with a = 0.296 and r = 0.001. Since | r | < 1, the series iconvergent          with limiting sum 

Since 296 = 8 x 37 and 999 = 27 x 37, this fraction is in its simplest form 8/27.



Arithmetic Sequences

An Arithmetic sequences, or arithmetic progression,is a sequence whose terms go up or down by constant steps.

The inductive definition for an arithmetic sequence has the form :

 where the number d is called the common difference.

Eg 1:                1    3    5    7    9  ...
                     first term a = 1 and common difference d = 3.

Eg 2:                1    4    5    7    8 ...

                     This is not an arithmetic sequences. No solutions,