Maths with Lemon

Geometric sequences

"Mathematics compares the most diverse phenomena and discovers the secret analogies that unite them."
— Joseph Fourier

Geometric Sequences

What you have to know :

You must be able to manipulate algebraic expressions
(If not, check this lesson)
You must be able to manipulate exponential expressions.
(If not, check this lesson)
You must be able to solve simultaneous equations.
(If not, check this lesson)

Key Points

1. Watch the video:

2. Read this presentation
3. Watch this solved problem

Extra

Material and references:

Hodder Book SL(ISBN: 9781510462359) :
2B

Key Points

1. You should know the formula for the \( n \)th term of a geometric sequence: \[ u_n = u_1 r^{\,n-1}. \]
2. You should know the two versions of the formula for the sum of the first \( n \) terms of a geometric sequence:
\[ S_n = \frac{u_1(1 - r^n)}{1 - r}, \quad r \ne 1 \] or
\[ S_n = \frac{u_1(r^n - 1)}{r - 1}, \quad r \ne 1. \]

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