# 2 integration method giving different results? Where did I go wrong?

• Apr 22nd 2010, 06:54 PM
chengbin
2 integration method giving different results? Where did I go wrong?
$\int 2(x+1)dx$

Method 1

$u=x+1$
$du=dx$
$\int 2udu$
$u^2+c$
$(x+1)^2+c$

Method 2

$\int (2x+2) dx$
$x^2+2x+c$

???
• Apr 22nd 2010, 06:59 PM
skeeter
Quote:

Originally Posted by chengbin
$\int 2(x+1)dx$

Method 1

$u=x+1$
$du=dx$
$\int 2udu$
$u^2+c$
$(x+1)^2+c$

Method 2

$\int (2x+2) dx$
$x^2+2x+c$

???

both are correct ... they only differ by a constant.