## IB Maths HL Series

Discussions for the Core part of the syllabus. Algebra, Functions and equations, Circular functions and trigonometry, Vectors, Statistics and probability, Calculus. IB Maths HL Revision Notes

### IB Maths HL Series

IB Mathematics HL – Arithmetic Series

How can I find the sum of the first 15 terms for the sequence defined by the following formula?
$u_{n}=-2+8n$

Thanks
Max

Posts: 0
Joined: Mon Jan 28, 2013 8:06 pm

### Re: IB Math HL Series

IB Mathematics HL – Arithmetic Series

This is an arithmetic sequence with common difference d = 8.
The first term is 6, common difference is d = 8, and n =15.
To find the sum of the first n terms, you will use the following formula for a
arithmetic series:

$S_{n}=\frac{n}{2}[2a+(n-1)d]$

where $a=6, d=8, n=15$

So
$S_{15}=\frac{15}{2}[2(6)+(15-1)8]= \frac{15}{2}[12+(14)8]=$

$= \frac{15}{2}[124]=62(15)=930$

Hope these help!!
miranda

Posts: 268
Joined: Mon Jan 28, 2013 8:03 pm

### Re: IB Maths HL Series

Thanks miranda!!
Max

Posts: 0
Joined: Mon Jan 28, 2013 8:06 pm