The sum of n terms of an AP is (5n² – 3n). Find the AP and hence find its 10th term.
Answers
Answered by
14
Answer:
AP:2,12,22.......92
a10=92
Explanation:
Sum of the n terms of an A.P. is 5n2 - 3n. Find the terms of the A.P. and also find the 16th term.
Sn = 5n2 - 3n an = Sn - Sn - 1
an = 5n2 - 3n - [5(n - 1)2 - 3 (n - 1)]
an = 5n2 - 3n -[5(n2 - 2n + 1) - 3n + 3]
an = 5n2 - 3n - 5n2 + 10n - 5 + 3n - 3
an = 10n - 8
a1 = 2
a2 = 20 - 8 = 12
a3 = 30 - 8 = 22
a10=100-8=92
Hope this helps.....
Answered by
19
Answer:
92
Explanation:
Sn=5n²-3n
Putting n=1, 5n²-3n
=5-3=2
Putting n=2, 5n²-3n
=14
Therefore 2nd term is 14-2=12
Therefore AP is 2, 12, 22 ... and so on.
nth term = a+(n-1)d
10th term=a+9d
=2+9*10
=2+90
=92
Similar questions