Question

Find the first four terms of the sequence given a1=−9 and an+1=an+n

Answer 1

a1 =-9

a2=(-9) + 1

a3 =(-9)+ 1 +1

a4 = (-9)+1 +1 +1. ......

an+1 =an+n

a1 +1 = a1 +1

a2 +1 = a2 +2

a3 +1 = a3 +3

a4 +1 = a4 +4......

Answer 2

Correction in question:

Find the first four terms of the sequence given a1 = −9 and an + 1 = a + n.

Answer

a = -9

an + 1 = a + n

=> an = a + n - 1

=> a2 = -9 + 2 - 1

=> a2 = -8

d = a2 - a = 1

Terms = -9, -8, -7, -6...