Question

this is an equal to 3 and square minus n is a sum of n term of an ap determine the AP and its 24th term. Plz do this fast

Answer 1

Step-by-step explanation:

Given S

n

=3n

2

−n

Then S

n−1

=3[3(n−1)]

2

−(n−1)

a

n

=S

n

−S

n−1

⇒a

n

=[3n

2

−n]−[3(n−1)

2

−(n−1)]

=3[n

2

−(n−1)

2

]−n+n−1

=3(n

2

−n

2

+2n−1)−1=3(2n−1)−1=6n−4

Then, a

25

=6×25−4=150−4=146