Question

The sum of the 1st n terms of an AP is 5n-n2 Find the nth term of an A.P

Answer 1

n/2(2a+(n-1)d)=5n-n^2
a+(n-1)d/2=5-n
(a-d/2)+nd/2=5-n
comparing
d/2=-1
d=-2
a-d/2=5
a+1=5
a=4
nth term
=a+(n-1)d
=4+(n-1)(-2)
=4+2-2n
=6-2n