Question

Find the sum of first 20 terms of the list of numbers whose nth term is given by an=3-4n

Answer 1

nth term = 3-4n

1st term = 3-4×1 = -1

20th term = 3-4×20 = -77

Sum of first 20 terms = 20/2(-1+-77)

= 10×-78

= -780

Answer 2

Answer:- 9

Step-by-step explanation:

Given an = 3 + 2n

Now 1st term = ax = 3 + 2 (1) a = 3 + 2 a = 5

2nd term = a? = 3 + 2 (2)

= 3 + 4 = 7

3rd term = a3 = 3 + 2 (3) = 3 + 6

Hope it helps  you

Pls mark me brainliest