Question

Given a=7,a13=35 find d and s13

Answer 1

a=7

a13=35

i.e a+12d=35      

7+12d=35    

12d=28           

d=28/12=7/3    

s13=n/2(a+a13)          

=13/2(7+35)            

=13*42*½            

=13*26          

=338

Answer 2

Answer:

a=7

a13=35

∴a+12d=35

7+12d=35

12d=35-7

12d=28

∴d =7/3

Now ,Sn=n/2[2a+(n-1)d]

∴S13=13/2[2×7+(13-1)7/3]

=13/2[14+28]

=13/2×32

=13×32

=208

∴d= 7/3 and  S13=208

Step-by-step explanation: