Question

Find the sum of the first 20 terms of the arithmetic sequence 4, -4, -12, -20​

Answer 1

Answer:

an=20

a=4

d=a2-a1

=-4-4

=0

Step-by-step explanation:

formula

an=a+(n-1)×d

20=4+(n-1)×0

20-4=n-1

16=n-1

n=16+1

n=17

17 is the answer