# Thread: Finding area under a function using alegbraic integration

1. ## Finding area under a function using alegbraic integration

Hi,

I have to integrate a function and find the area underneath it. I think I've followed the procedure correctly but the numbers that I got are really strange, if anyone can help me I wud greatly appreciated it.

P.S. If anyone has time to look at an earlier qustion that I posted that would also be greatly appreciated.[/FONT]

http://www.mathhelpforum.com/math-he...ven-point.html

2. I'm not really sure if you integrated that.

I did this (I wrote it on the back of my notepad):

Is that the right question?

Also what you've written doesn't make 0.4

0.1x(10^2)x4x10+1=401

0.1x0x4+1=1

401-1=400?

What's the part that you've written under the question as well?

You also missed the "dx" after the integral.

I assumed you were just integrating with respect to x.

3. That seems to make sense, it certainly is more in line with what I've found using a calculator to find the answer.

As for whats under the question, I'm not so sure I know what you mean there.

Perhaps it would also help if I listed the original question

Calculate the function ( $0/10x^2+4x+1$) by algebraic means; ie calculate the exact integral of your chosen function over your chosen domain.

The domain which I am using is 0 to 10 along the x axis.

P.S. I accidentally used multiplication symbols instead of addition symbols in my original question.

Thanx for all the help BTW

4. I meant the bit with the ln (log with a base e). I couldn't really see to which part that applied since I thought there wasn't a l/x present.

Are you sure you mean 0? That would just make the integral of 0 that would just be 0.

Could the question be:

?

That integral is rather hard to do though

5. Hmmm I get what you mean about the 0. I can change that to a 1 seeing how as I can choose my own function (within certain limitations). As for the log, its basically just what the rather vague explanation in my textbook said.

6. So you chose the function:

?

It is pretty hard since the quadratic can't be factorised (complex solutions) so partial fractions cannot be used. The differential of the denominator isn't on the top so natural logs are also out.

If you can choose your own function, why don't you choose something easy???? =O

7. Indeed I would If I could, but I have to complete it by tomorrow morning and I have used the function to differentiate it using Left and Right Riemann Sums, the Monte Carlo Method, the Midpoint Rule, The Trapeziod rule and Simpson's rule and changing the function would require re-doing all of these processes as well.

8. wow, well I have no idea how to integrate that.

Could you just write underneath all your working "this can't be integrated" and leaving it at that?

If you put an x as the numerator it becomes a bit easier.

9. fraid not. Thanx for your help tho. I might just leave the process as is, take the loss in marks and hope that I get some for implementing the process at least partially correctly if I can't figure it out thru looking more in my text book.