Question

Hello friends ☺️☺️

plzz answer my question plzzzz

in an AP, the first term is 25 , nth term is -17 and the sum to first n terms is 60. find the common difference.

l will mark u as brainliest answer ☑️☑️

Answer 1

Answer:

d = -3

Step-by-step explanation:

Let 'a' be the first term and 'd' be the common difference.

First term (a) = 25.

nth term (an) = l = -17.

Sum to first n terms (Sn) = 60.

(i)

We know that Sum of n terms of an AP sn = (n/2)[a + l]

60 = (n/2)[25 - 17]

60 = (n/2)[8]

60 = 4n

n = 15.

(ii)

We know that nth term of an AP an = a + (n - 1) * d

-17 = 25 + (15 - 1) * d

-17 - 25 = 14d

-42 = 14d

d = -3.

Therefore, Common difference = -3.

Hope it helps!

Answer 2

Answer:

-3

Step-by-step explanation:

Sn=n/2(a+an)

60=n/2(25+(-17))

60=n/2(8)

60×2/8=n

n=15

now

an=a+(n-1)d

-17=25+(15-1)d

-17-25=14d

d=-42/14=-3

so,

n=15

d=-3