Question

Page
1 The sum of
the third and seventh terms of an Ap.
is 6 and
their product is 8. Find the sum at
first sixtees terns of the AP​

Answer 1

Step-by-step explanation:

let a is the 1st term and d is the common difference of the AP series

so, 3rd term = a +(3-1).d=a+2d

7th term= a+(7-1).d=a+6d

3rd term+7th term =6

=> a+2d+a+6d=6

=> 2a+8d=6

=> a+4d=3

again,

(a+2d)(a+6d)=8

(a+4d-2d)(a+4d+2d)=8

=> (3-2d)(3+2d)=8

=> (3)^2-(2d)^2=8

=> 9-4d^2=8

=> -4d^2=8-9= -1

=> 4d^2=1

=> d^2=1/4

=> d=+1/2 , -1/2

a=3-4d=3-4.1/2=3-2=1

so, sum of first 16 th term

=16/2{2a+(16-1).d}

=8{2.1+15.1/2}

=8(2+15/2)

=8.19/2

=4.19

=76

Answer 2

Answer:

sum of 16 terms of ap would be 122 or - 324

HOPE IT WILL HELP YOU