Question

the first term of an arithmetic progression a_1,a_2,a_3,....equal to unity. At what value of difference of the progression is a_1a_3+a_2a_3 is minimum

Answer 1

let a2 =a
then a1 = a-d
a3 = a+d

we are given a-d =1

we need to minimize
(a-d)(a+d) + a(a+d)

easier now sire?

Answer 2

thanks a lot..

Answer 3

Glad I could help.