What is the sum of the geometric sequence -1, 6, -36, if there are 7 terms? a) -39,991 b) -6,665 c) 6,665 d) 39,991

The formula of a sum of the geometric sequence:

Calculate r (common ratio):

Substitute:

A) -39,991

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

question 1: step-by-step explanation:

1/4 of 84 = 84÷4= 21