# Thread: Not sure if this is correct...

1. ## Not sure if this is correct...

Okay well I have a definite integral with a square root and u of x-1, with x on the outside and a,b values 1,3.

I changed (sqrt)x-1 to (x-1)^1/2 and divided the x by x to get u' or 1, leaving an x on the outside of the integral. I also changed the a,b values to 0,2. and came out with the answer 3x/2 (x-1)^3/2 before continuing is this correct? I just would like to make sure because I have never gotten a problem like this.

Okay well I have a definite integral with a square root and u of x-1, with x on the outside and a,b values 1,3.

I changed (sqrt)x-1 to (x-1)^1/2 and divided the x by x to get u' or 1, leaving an x on the outside of the integral. I also changed the a,b values to 0,2. and came out with the answer 3x/2 (x-1)^3/2 before continuing is this correct? I just would like to make sure because I have never gotten a problem like this.
Is this the integral that you are trying to sovle?

$\int_{1}^{3}x\sqrt{x-1}dx$

If so, I would let $u=x-1$ like you said, then sub. $u+1=x$ back in for x. Then integrate from there, after changing the limits like you said.

3. Originally Posted by McScruffy
Is this the integral that you are trying to sovle?

$\int_{1}^{3}x\sqrt{x-1}dx$

If so, I would let $u=x-1$ like you said, then sub. $u+1=x$ back in for x. Then integrate from there, after changing the limits like you said.
okay so I was right, got the same answer