Question

When
$5 {n}^{2} + 2n$
Is n th term
Find Sn-1​

Answer 1

Answer:

Sorry

Step-by-step explanation:

But I dont understand Maths

Answer 2

There is a simple trick to finding the nth term of a series whose sum upto n terms is given.

nth term = (sum of n terms) - (sum of n-1 terms)

According to the given formula, Sum of n terms is 5n^2 + 2n and that of n-1 terms is 5(n-1)^2 + 2(n-1)

Thus, nth term = 5[n^2-(n-1)^2] + 2[n-(n-1)]

= 5[(n+n-1)(n-(n-1))] + 2(1)

= 5(2n-1)(1) + 2

= 10n-3

.

.

.

.

.

.

.

.

.

.

.

#the great Shreya ❤️