How many terms are in the arithmetic sequence 7, 1, −5, …, −161?
1 answer:
Answer:
29
Step-by-step explanation:
The n th term of an arithmetic sequence is
• = a₁ + (n - 1)d
where a₁ is the first term and d the common difference
d = 1 - 7 = - 5 - 1 = - 6 and a₁ = 7, = - 161, hence
7 - 6(n - 1) = - 161 ← solve for n
7 - 6n + 6 = - 161
13 - 6n = - 161 ( subtract 13 from both sides )
- 6n = - 174 ( divide both sides by - 6 )
n = 29
There are 29 terms in the sequence
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Answer:
8 years
Step-by-step explanation:
Let age of father be f
age of John be j
age of Alice be a
John's father is 5 times as old as John. We can write:
f = 5j
John is twice as old as Alice. We can write:
j = 2a
or
a = j/2
SUM OF ALL OF THEIR AGES (after 2 years) will be 58. We can write:
f+2 + j+2 + a+2 = 58
This becomes:
f + j + a + 6 = 58
f + j + a = 52
Now, we replace third equation with the first two (in bold) and get:
So John is 8 years old
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