The first four terms of sequence is 20, -10, -40, -70
Solution:
Given that we have to find the first four terms of sequence
Given recursive formula is:

To find the first term, substitute n = 1

Thus the first term of sequence is 20
To find the second term, substitute n = 2

Thus the second term of sequence is -10
To find the third term, substitute n = 3

Thus the third term of sequence is -40
To find the fourth term, substitute n = 4

Thus the first four terms of sequence is 20, -10, -40, -70