Dr. J's Maths.com
Where the techniques of Maths
are explained in simple terms.

Sequences & Series - Sigma notation.
Test Yourself 1 - Solutions.


 

 
General interpretation. 1. 2.
  3. 4.
  5. 6.
     
     
Use with arithmetic series. (i) is an arithmetic series because the model is a linear equation and the common difference is the gradient
(i.e. 4).

OR

The series is 13 + 17 + 21 + ... 61 which has a common difference of 4. So the series is arithmetic.

(ii) Hence evaluate this summation.

T1 = 13; n = (15-2); T13 = 61.

When k = 4, the term is 17 and we have a common difference of 6 (coefficient of the expression after sigma sign).
     
     
Use with geometric series.  
  16.