Question

The nth term of an A .P os given by t=4n-5.Find the sum of the first 25 Terms of the A P

Answer 1

hola there,
if n=1
an= 4(1)-5 =-1
if n=2
an=4(2)-5 =3
therefore a= -1 ,a2= 3.... is the ap
d= 3-(-1) = 4
if n=25
an=4(25)-5 = 95
S25= n/2(a+an)
25/2(-1+95)
25/2(94) =25(47)=
1175
there fore th e sum of first 25 no og the ap will be 1175

❤hope it helps

Answer 2

heya,,

let n=1

then,t1=4*1-5

t1=-1

and again let n=2

t2=4*2-5

then, t2=3

so,d=t2-t1

3-(-1)

d=4

so,,...
sm=n/2[2a+(n-1)d

s25=25/2【-2+24*4】

s25=47*25

s25=1175.ans

hope it help you.

.@rajukumar☺