Solve S=n/2 (a+b) for b
1 answer:
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Answer: graph E.
A geometric sequence can be written as:
where:
a₁ = first term = 4
r = ratio = 0.5
Substituting the numbers, we have:
or else
This is an exponential function with base less than 1. Therefore, we can exclude graph C (which depicts a linear function), and graphs A and D (which depict an exponential function with base greater than 1).
In order to choose between graph B and E, let's evaluate the function in two different points:
Therefore, we need to look for the graph passing through the points (1, 4) and (2, 2). That is graph E.
Answer:
S₁₅ = 645
Step-by-step explanation:
The sum to n terms of an arithmetic sequence is
=
[ 2a₁ + (n - 1)d ]
where a₁ is the first term and d the common difference
Using the nth term formula = 5n + 3 , then
a₁ = 5(1) + 3 = 5 + 3 = 8
a₂ = 5(2) + 3 = 10 + 3 = 13 , then
d = a₂ - a₁ = 13 - 8 = 5
Thus
S₁₅ = [ (2 × 8) + (14 × 5) ]
= 7.5( 16 + 70)
= 7.5 × 86
= 645