<u>Answer:</u>
The correct answer option is B. ![S _ n = a _ 1 [ \frac { 1 - r ^ n } { 1 - r } ]](https://tex.z-dn.net/?f=%20S%20_%20n%20%3D%20a%20_%201%20%5B%20%5Cfrac%20%7B%201%20-%20r%20%5E%20n%20%7D%20%7B%201%20-%20r%20%7D%20%5D%20)
.
<u>Step-by-step explanation:</u>
The following is the formula that is used to find the sum of a geometric progession:
where 
is the sum, 
is the first term, 
is the common ratio while 
is the number of terms.
5 cars and 9 motorbikes had their tires changed.
38÷4= 9.5 motorbikes
14-9=5 cars
9×2=18 5×4= 20 (add together) = 38 tires
Perpendicular Bisector Theorem
The notation of a bar (vinculum, or overbar) over a whole number
doesn't seem to be very common. Here are some possibilities as to
what it could mean:
It is sometimes used as a grouping symbol, as in a fraction:
_____ __
3 + 1 x 5 = 20 so 67 = 67
I have also seen it used to refer to the average:
_ __
x = {1,2,6}, x = 3 so 67 = 67
(the average of one number is itself, of course).
I have also heard that it can be used to mean "1000 times whatever is
underneath", especially with Roman numerals - see the following Web
page, Final Answers by Gerard P. Michon:
To find f(-20), first figure out which piece x = -20 fits with.
Since -20 < -12, x = -20 first in the domain used by the third piece.
For f(-20), treat this function as if it was just f(x) = 3x-7.
f(-20) = 3(-20) -7
= -60 - 7
= -67
