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the question is 

When  x3+ 30x - c is divided by x-5 the remainder is 5. What is c?

i know how to divide polynomials, but i didn't understand how to work backwards in this situation. or, should i solve it a different way? thank you!

 Apr 23, 2020
edited by heyhey  Apr 23, 2020
 #1
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If you can do long division, divide  x3 + 30x - c  by  x + 5.

You get a quotient of  x2 - 5x + 55.

Then you will have to subtract  275  from  -c  to get a remainder of 5.

The only value that  -c  can have is  280  which means that   c  must equal to  -280.

 Apr 23, 2020

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