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

Answer 1

Given information: a(1)=-9 and a(n+1)=an+n

When n = 1: a(1+1) =a(1) +1

a(2) = -9 +1

a(2) = -8

When n = 2: a(2+1) =a(2) + 2

a(3) = -8 + 2

a(3) = -6

When n = 3: a(3+1) = -6 + 3

a(4) = -3

Answer 2

a₁ = -9

a₂ = a₁ + 2

a₂ = -9 + 2

a₂ = -7

a₃ = a₂ + 3

a₃ = -7 + 3

a₃ = -4

Can you do a₄?