Question

The sum of first n terms of a sequence is n(n+1), then the tenth term of the sequence is :
be quick pls I will give points​

Answer 1

ɢɪᴠᴇɴ:

Sum of the n terms= n(n+1)

ᴛᴏ ꜰɪɴᴅ:

Tenth term

ꜱᴏʟᴜᴛɪᴏɴ:

Sum of the 1st 1 term, a1

= 1(1+1)

= 1× 2

= 2

Sum of the 1st 2 term,a1+a2= 2(2+1)

a1+a2= 2× 3

2 + a2= 6

a2= 6-2

a2= 4

common difference, d = a2-a1

= 4-2

= 2

We know that,

nth term = a+(n-1)d

Tenth term = a1+(10-1)d

= 2+ 9(2)

= 2+ 18

= 20