Question

help me i need to pass my test PLease
The first term of a geometric series is 3, and the sum of the first term and the second term is 15. What is the sum of the first six terms?

Answer 1

The first term is 3. The second term is 3 multiplied by the common ratio r. So we can write an equation from the given value of the sum of the first and second terms:
15 = 3 + 3r
This equation can be solved to find the value of r. Can you do that?

Answer 2

r=4

Answer 3

What about terms 3-6?

Answer 4

Good work! Now that you have the value of r you can use the following formula to find the sum of the first six terms:
\[S _{n}=\frac{a(r ^{n}-1)}{r-1}\]

Answer 5

28.2

Answer 6

a.1023
b.3906
C4096
d.11718
these are the options

Answer 7

2457

Answer 8

but its the choses i am given

Answer 9

Sorry, my bad. Substituting in the formula for the sum of n terms gives the following:
\[S _{6}=\frac{3(4^{6}-1)}{4-1}=4^{6}-1=4095\]

Answer 10

thabks

Answer 11

You're welcome :)