Trouble With Polynomial Problem

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Piglover

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Mar 28, 2020
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3
Hi,


I am working on the problem below:

What is the volume of this same piece of luggage if its height is x+1?
Remember: Volume= (length)(width)(height)

V= (3x-5)(2x+1)(x+1)

I believe that the polynomials are supposed to be multiplied in order to determine the volume and I am not sure how to do this. I attempted this problem but the only solution I came up with was 7x-3 which seems to be incorrect as I got to that answer by adding the polynomials. How do you multiply these polynomials in order to determine the area?

Thank you!
Piglover
 
Yes use the method in Post#2 to expand out (3x-5)(2x+1) and then multiply the result by (x+1).
Don't try to do it all at once.
 
Why would you add when you think that you should multiply? Also 3x+2x+x=6x not 7x.

Most importantly you need to understand equality better. If you think that (3x-5)(2x+1)(x+1) = 7x-3 you can check that. Remember that you have or think you have equality. That is the lhs of the equal sign and the rhs of the equal are well equal all the time.

So you can assume x=0 (or any number you like). Now the lhs will be (-5)(1)*1) = -5 while the rhs will be -3. Now you know that what you have is not correct.
 
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