Question

if the first ,second and last terms of AP are abc then the sum is

Answer 1

sum of three terms of ap
=3/2a+c

Answer 2

First term(a) = a
Second term : b = a+d
Common Difference (d) = (b-a)
Last term(l) = c
c = a+(n-1)(b-a)
n = (c-2a+b)/(b-a)
Sum :- n/2 (a+l)
= (c-2a+b)/2(b-a) × (a+c)
= {(b+c-2a)(a+c)}/2(b-a)