Question

in an ap the sum of its first n terms is 6n-n^2.Find its 25th term

Answer 1

hey mate

here is your answer

when n=1

s=n/2(2a+(n-1)d)

6*1-1²=1/2(2a+(1-1)d)

5=1/2(2a)

=5=a

when n=2

6*2-2²=2/2(2*5+(2-1)d)

8=(10+d)

d=-2

therefore

25th term=5+24*-2

=-48+5

=-43