Question

given a = 7, a13 = 35. find d and S13​

Answer 1

Answer:

This is the answer:

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

.

Answer 2

Answer:

a=7

a13=35

since n=13

now,

an=a+(n-1)d

35=7+(13-1)d

35-7=12d

28=12d

28/12=d

d=7/3

now we know that

sn=n/2(a+an)

hence we get

s13= 13/2(7+35)

s13=13/2*42

s13=273