This type of sequence is called Geometrical Progression (GP).
GP = a + ar + ar^2 + ar^3 .........
In this a is the first term and r is the constant ratio between terms
As per the question a = 5 and r = -2
f = 5 -10 + 20 - 40 ....
5, -1, -7, -13, -19
-6 -6 -6 -6 the difference between the numbers is -6
; where a₁ is the first term, d is the difference, and n is the term
f(1) = 5
= 11 - 6
= 5
TRUE
a_n = 11 - 6n
Step-by-step explanation:
you can observe every next element is smaller then the previous one by 6
a_n = 5 - 6*(n-1)
a_n = 5 - 6n + 6
The given sequence is
5,–1, –7, –13, –19, ...
And here each current term is the sum of previous term and -6. That is
It means
current term is the difference of previous term and 6, so we will get
Therefore the correct option is the third option .
Remark
Start with the ones that are wrong because they are in the wrong order.
To find F(n + 1) in a recursive formula, it must be by itself on the left. That makes B wrong.
Find out the difference in the sequence
You are subtracting 6 from the current term to get to the next term. There is no multiplication anywhere. That makes D wrong.
Now to distinguish A and C, you have to decide between addition and subtraction
You are subtracting 6 from the current term to get to the next one.
C <<<<< Answer
, where and
The terms of the sequence are:
The first term of this sequence is .
There is a constant difference among the terms.
This constant difference can determined by subtracting a previous term from a subsequent term.
The general term of this arithmetic sequence is given recursively by
We substitute the necessary values to obtain:
Or
f(n+1) = f(n) - 6
Assume your sequence is
5, –1, –7, –13, –19, …
A recursive formula defines each term of a sequence using the preceding term.
For your sequence,
f(2) = -1
f(3) = -7
f(4) = -13
f(5) = -19
We see that
f(2) - f(1) = -1 - 5 = -6
f(3) - f(2) = -7 - (-1) = -6
f(4) - f(3) = -13 - (-7) = -6
f(5) - f(4) = -19 - (-13) = -6
Each term is six units less than the preceding term.
The repeating pattern (recursive formula) is
f(n + 1) - f(n) - 6 or
f(n+ 1) = f(n) - 6
It will provide an instant answer!