If a, b, c from an AP with common difference d, then the value of a-2b-c is equal to
(3)
a,b,care in AP with common difference =d∴ b-a=c-b=d⇒b-a=d⇒a=b-d⇒b=a+dand c-b=d⇒c=b+d⇒c=a+2dNow,a-2 b-c=a-2(a+d)-(a+2d)=a-2a-2d-a-2d=-2a-4d