Question

1. Given the below sequence: -1, -3, -5, -7, . . . (a) What are the next 3 terms? (b) Is this an arithmetic or geometric sequence? (c) Why? (d) What is the 27th term? (Show how to find it and tell me what the 27th term is.)

Answer 1

Answer:

(a) -7 , - 9 , - 11

(b) Arithmetic sequence

(c) There is a common difference of -2

(d) -53

Step-by-step explanation:

(a) To find the next three terms , we must firs check if it is arithmetic sequence or a geometric sequence . For it to be an arithmetic sequence , there must be a common difference :

check :

-3 - (-1) = -5 - (-3) = -7 - (-5)  = -2

This means that there is a common difference of -2 , which means it is an arithmetic sequence.

The next 3 terms we are to find are: 5th term , 6th term and 7th term.

$t_{5}$ = a + 4d

$t_{5}$ = - 1 + 4 ( -2 )

$t_{5}$ = -1 - 8

$t_{5}$ = - 9

6th term = a +5d

$t_{6}$ = -1 + 5(-2)

$t_{6}$ = -1 - 10

$t_{6}$ = - 11

$t_{7}$ = a + 6d

$t_{7}$ = -1 + 6 (-2)

$t_{7}$ = -1 - 12

$t_{7}$ = -13

Therefore : the next 3 terms are : -9 , -11 , - 13

(b) it is an arithmetic sequence because there is a common difference which is -2

(c) Because of the existence of common difference

(d) $t_{27}$ = a + 26d

$t_{27}$ = -1 + 26 ( -2 )

$t_{27}$ = -1 - 52

$t_{27}$ = - 53