Question

Solve this problem.​

Answer 1

Step-by-step explanation:

A2 =2 and A7=22and n=35

we know that,

A2= a+b=2...(i)

and A7=a+6d=22...(ii)

solving the linear equation (i)and(ii), we get

a+d-a-6d=2-22

=-5d=-20

d=4

putting the value of d in equation (i) we get

a+4=2

=a=2-4=-2

now,we have to find the sum of first 35 terms

Sn = n\2(2a+(n-1)d)

S35=35\2[2×(-2)+(35-1)4]

S35 = 35\2[-4+34×5]

S35=35[-2+34×2]

S35=35[66]

S35=2210