Question

Find the sum of 15 terms of an ap whose nth term is 9_5n.

Answer 1

Answer:

-465

Step-by-step explanation:

n1=9-5(1)=4

n2=9-5(2)=-1

d=n2-n1=(-1-4)=-5

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

[a is nothing but n1]

Sn = 15/2(4+(15-1)(-5))

= -465

I guess it is 9-5n and not 9_5n