Help with easy intagration

1. Apr 13, 2005

whatdofisheat

i am haveing some trouble solvine a simple question
the question is what is the work done by the equation
8x-16
from 0 to 3
if you intagrate it you should get
4x^2 -16x
then you sub in zero get zero then you sub in 3 and get -28?
yet the answer in the book is -12 am i doing something wrong?
or is the book wrong?

2. Apr 13, 2005

estalniath

I think that you made a mistake in your calculations, subbing 3 in gives
4*(9)-48=36-48=-12 =)

3. Apr 13, 2005

whatdofisheat

thanks i knew it was a stupid thing im being an idoit

4. Apr 13, 2005

whozum

Pat yourself on the back for integrating correctly atleast :)

5. Apr 14, 2005

whatdofisheat

ya but if i cant times 3 by 16 correctly i think the intergration is the least of my worries

6. Apr 14, 2005

HallsofIvy

Would it be petty of me to point out that equations don't DO work?

What you mean I presume is that the force is given by F(x)= 8x-16 and moves an object from x= 0 to x= 3.

7. Apr 14, 2005

Theelectricchild

You make an interesting point, but keep in mind that many of these problems in math always have an answer that is dimensionless... Yes it is better to write the work done by some force moving a particle... but when the solutions key gives an answer with no units, that really annoys me... so I don't really see anything wrong with saying "the work done by an equation." Same with surface integrals... answers are dimensionless... which is why I like to see applications of math. What does it mean when a surface integral evaluates to "16pi"? What does it mean when the work done is "5" ?

8. Apr 15, 2005

whatdofisheat

yes its petty

9. Apr 15, 2005

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