Question

The sum of the 3rd and 7th term of sn ap is 6 and their product is 8. Find the sum if the first 16 term of the ap

Answer 1

Answer:

Let the first term be a and common difference be d 

nth term = a+(n-1)d 

Given Third Term + Seventh term = (a+2d)+(a+6d) = 6 ==> a+4d = 3 

hence, a= 3-4d 

Third Term * Seventh term = (a+2d)*(a+6d) = 8 

(3-4d+2d)*(3-4d+6d) = 8==> (3-2d)*(3+2d) = 8 

i.e. 9-4d^2 = 8==> d^2 = (9-8)/4 = 0.25==> d = 0.5 or -0.5