Mathematics

Problem

Let

\Delta(x) =

$x+a$	$x+b$	$x+a-c$
$x+b$	$x+c$	$x-1$
$x+c$	$x+d$	$x-b+d$

and

\int_0^1 \Delta(x)\,dx = -16

, where

a, b, c

and

d

are in AP, then the common difference of the AP is equal to a.

\pm 1

\pm 2

\pm 3

\pm 4