Answer:
The explicit form is 
Step-by-step explanation:
The explicit form of a geometric sequence is given by:

where an is the nth term, a is the first term of the sequence and r is the common ratio.
In this case:
a=162
The value of the common ratio is obtained by dividing one term by the previous term.
For the first and second terms:
108/162=2/3
For the second and third terms (In order to prove that 2/3 is the common ratio)
72/108=2/3
Therefore:
r=2/3
Replacing a and r in the formula:

Answer:
gnrg
Step-by-step explanation:
You need to give some form of an image for us to be able to give you the answer. There’s no way of solving the equation you’ve given us without the key information from the image....
One month = 5000
Number of months before the spark plugs need to change :
15000 ÷ 5000 = 3
The sparks can last 3 months before it needs to be changed.
Number of times it need to change in a year = 12 ÷ 3 = 4
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Answer : It needs to be change 4 times a year.
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