Question

In an AP : Given a = 7, 13 = 35, find d and 13​

Answer 1

Step-by-step explanation:

Hello Friend

as you have given

a=7

a¹³ = 35 it means no of terms = 13

so n = 13.

we know

aⁿ = a+(n-1)d

so put the values .----

35 = 7 +(13-1)d

28 = 12d

so

d = 28/12 => 7/3

Now sⁿ = n/2(a+aⁿ)

hence we get

sⁿ = 13/2(7+35)

=> 13/2(42)

=>21×13

=> 273