# Help verifying correct answer for definite integral problem

• May 6th 2009, 05:48 AM
ceb0196
Help verifying correct answer for definite integral problem
I am putting together my study guide for my calc final and I cannot get a hold of my prof to verify if my answer is right on this question from our last test:

Determine: integrand/b=4 a=-1 (2x+3)dx

I broke it up into two parts, on from -1 to 0 and one from 0 to 4 and my final answer is 26.

Any help verifying if this is correct would be very much appreciated.
• May 6th 2009, 05:51 AM
Banned for attempted hacking
Quote:

Originally Posted by ceb0196
I am putting together my study guide for my calc final and I cannot get a hold of my prof to verify if my answer is right on this question from our last test:

Determine: integrand/b=4 a=-1 (2x+3)dx

I broke it up into two parts, on from -1 to 0 and one from 0 to 4 and my final answer is 26.

Any help verifying if this is correct would be very much appreciated.

There is not point breaking it up it's not an improper integral.

integrand/b=4 a=-1 (2x+3)dx = (16 +12) -(1 -3) = 30
• May 6th 2009, 05:53 AM
ceb0196
I got the same numbers, but one of my signs was wrong. Thanks for clarifying for me.

She did instruct us to break it up from - to 0 and then from 0 to whatever. Is that not correct?? I did get the same numbers, but I don't want to start bad habits...
• May 6th 2009, 05:55 AM
Banned for attempted hacking
Quote:

Originally Posted by ceb0196
I got the same numbers, but one of my signs was wrong. Thanks for clarifying for me.

She did instruct us to break it up from - to 0 and then from 0 to whatever. Is that not correct?? I did get the same numbers, but I don't want to start bad habits...

It correct to do that, but there isn't any point.

Usually you only break it up when you have an improper integral.

You should do it the way you feel comfortable with, don't listen to me. :D
• May 6th 2009, 05:56 AM
skeeter
Quote:

Originally Posted by ceb0196
I am putting together my study guide for my calc final and I cannot get a hold of my prof to verify if my answer is right on this question from our last test:

Determine: integrand/b=4 a=-1 (2x+3)dx

I broke it up into two parts, on from -1 to 0 and one from 0 to 4 and my final answer is 26.

Any help verifying if this is correct would be very much appreciated.

$\int_{-1}^4 2x+3 \, dx$

$\left[x^2 + 3x\right]_{-1}^4$

$\left[4^2 + 3(4)\right] - \left[(-1)^2 + 3(-1)\right]$

$28 - (-2) = 30$
• May 6th 2009, 06:06 AM
ceb0196
Quote:

Originally Posted by ╔(σ_σ)╝
It correct to do that, but there isn't any point.

Usually you only break it up when you have an improper integral.

You should do it the way you feel comfortable with, don't listen to me. :D

Yeah, I can see that now. Thanks for clearing it up! http://www.mathhelpforum.com/math-he...cons/icon7.gif

Quote:

Originally Posted by skeeter
$\int_{-1}^4 2x+3 \, dx$

$\left[x^2 + 3x\right]_{-1}^4$

$\left[4^2 + 3(4)\right] - \left[(-1)^2 + 3(-1)\right]$

$28 - (-2) = 30$

Excellent, thanks!