What should be the first term and the common difference so that it’s 19th term is 77
a1= 129 and d = -3
a1 =-13 and d= 5
a1 =112 and d = -2
a1=-14 and d =6
a1 = -13 and d = 5
The formula for the nth term of an arithmetic sequence is given by: an = a1 + (n-1)d
When n = 19, and a19 = 77:
77 = -13 + (19-1)5
77 = -13 + 18(5)
77 = -13 + 90
77 = 77
Therefore, the first term a1 should be -13 and the common difference should be 5 in order for the 19th term to be 77.