Question

Find S7of the sum of the geometric series.a1=−4374,a7=−6,r=1/3

Answer 1

Answer:

The sum of the first 7 terms in the geometric sequence is -6558

Step-by-step explanation:

s7 refers to the sum of the first 7 terms of the geometric sequence

To calculate the sum of terms, we use the sum of terms formula

We have this generally given as;

Sn = a(1-r^n)/(1-r)

a refers to the first term, given as a1 which is -4374

r is the common ratio which is 1/3

n is the number of terms, which is 7

substituting these values;

s7 = -4374(1-(1/3)^7)/(1-1/3)

s7 = -4374(1-(1/3)^7)/2/3

s7 = (3 * -4374)/2 * (1- (1/3)^7

s7 = -6561 * (1-1/2187)

s7 = -6561 * (2187-1)/2187

= -6561 * 2186/2187

= -6558