Question

Find the first five terms of the sequence. an=-n2+2n

Answer 1

If your sequence is this

`an = - {n}^(2) + 2n \\ then \\ a1 = - 1 + 2 = 1 \\ a2 = - 4 + 4 = 0 \\ a3 = - 9 + 6 = - 3 \\ a4 = - 16 + 8 = - 8 \\ a5 = - 25 + 10 = - 15`

Answer 2

The first five terms of the given sequence is 1, 0, -3, -8, -15

Explanation:

Given: nth term of sequence
`a_n=-n^2+2n`

We have to find the first five terms of the given sequence,

Consider the given nth term of sequence
`a_n=n^2+2n`

Substitute n = 1 ,

we get,
`a_1=-(1)^2+2=-1+2=1`

Substitute n = 2 ,

we get,
`a_2=-(2)^2+2(2)=-4+4=0`

Substitute n = 3,

we get,
`a_3=-(3)^2+2(3)=-9+6=-3`

Substitute n = 4 ,

we get
`a_4=-(4)^2+2(4)=-16+8=-8`

Substitute n = 5 ,

we get
`a_5=-(5)^2+2(5)=-25+10=-15`

Thus, first five terms of the given sequence is 1, 0, -3, -8, -15