The common ratio of a geometric series is 3 and the sum of the first 8 terms is 3280.
What is the first term of the series?

Step-by-step explanation:

The formula for calculating the sum of a Geometric series if the common ratio is greater than 1 is given as :

=

Where  is the sum of terms , a is the first term , r is the common ratio and n is the number of terms.

From the question:

= 3280

a = ?

r = 3

n = 8

Substituting this into the formula , we have

3280 =

3280 =

Multiply through by 2 , we have

6560 = a ( 6560)

divide through by 6560, we have

6560/6560 = a(6560)/6560

Therefore : a = 1

The first term of the series is thus 1

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Step-by-step explanation:

answer: i believe the answer is e

step-by-step explanation:

x =-.20752

step-by-step explanation:

4^(x+2)=12

4^(x+2)=12

take the log base 4 on each side

log 4 (4^(x+2) = log 4(12)

we know log b(a^y) = y log b (a)

(x+2) log 4(4) = log 4 (12)

x+2 = log 4 (12)

we know   logb c = loga c/loga b

we want to convert to base 10   so a = 10

by default, we do not write the 10   c = 4   and b = 10

log4 10 = log 12/log 4

log4 10 = log 12/ log 4

x+2 = log 12/ log 4

subtract 2 from each side

x +2 -2 = log 12/ log 4 -2

x = 1.79248125 -2

x =-.20752