# Thread: find or evaluate the integral

1. ## find or evaluate the integral

Hi

$\displaystyle \displystyle \int \frac{1}{1 + \sqrt{x}}~dx$

I have tried multiplying the numerator with $\displaystyle +\sqrt{x}$ and $\displaystyle -\sqrt{x}$ to factor out the denominator and got stuck
I have tried substituted $\displaystyle 1 + \sqrt{x}$ and got stuck
I have tried substituting $\displaystyle \sqrt{x}$ with u and replaced the numerator with $\displaystyle u - \sqrt{x}$ and came up with nothing...

2. Originally Posted by ugkwan
Hi

$\displaystyle \displystyle \int \frac{1}{1 + \sqrt{x}}~dx$

I have tried multiplying the numerator with $\displaystyle +\sqrt{x}$ and $\displaystyle -\sqrt{x}$ to factor out the denominator and got stuck
I have tried substituted $\displaystyle 1 + \sqrt{x}$ and got stuck
I have tried substituting$\displaystyle \sqrt{x}$ with u and replaced the numerator with$\displaystyle u - \sqrt{x}$ and came up with nothing...

use $\displaystyle u = \sqrt {x}$ so $\displaystyle du = \frac {1}{2\sqrt{x}}$

so now your integral will be

$\displaystyle \displaystyle 2\int \frac {u}{u+1} du = \displaystyle 2 \int (1 - \frac {1}{1+u} ) du$

can you continue from here ?

3. so what is the antiderivative of $\displaystyle \frac {u}{u+1}$?

4. nevermind my previous question. I figured out that by adding 1 and minusing 1 to the numerator, i can split the function, and then proceed with the antiderivative process.