Question

Consider this sequence: -81, -54, -36, -24, … . The sequence is . The common ratio of the sequence is . The sum of the first five terms of the sequence is .

Answer 1

The reason for the decreasing sequence is
`(2)/(3)`

the sum of the sequence is -243

Explanation:

Note that the numbers are decreasing so we will use the following formula to find the sum:

S∞=
`(t1)/(1-q)`,

where t1 is equal to the first number of the sequence and q is the reason that gives the following results.

to find q this form is used;

q=
`(t2)/(t1)= (-54)/(-81) =(2)/(3)`

then we replace in the formula of the sum to find the total