Electric field caused by a uniform linear charge

[gotem3303]

A uniform linear charge density of \lambda = 2.0 nC/m is distributed along the x-axis from x = 0 to x =3m. Which integral is correct for the magnitude of the electric field at x = -4 m on the x axis?
I'm going over a old test and he didn't circle the correct answer but I'm trying to understand the denominator.
I'm pretty sure I have everything but the denominator, would it be \int\frac{18dx}{(4+x)^{2}} from 0 to 3?

 

[Redbelly98]

Looks okay, except that you did not write any of the units.