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Hi everyone! Can anyone help me with this question?

 

When x^3 + 30x - c is divided by x - 5 the remainder is 5. What is c?

 

Thanks so much in advance!

 Dec 9, 2019
 #1
avatar+12 
+2

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Well, since we know the remainder is 5, We can see that x3+30x-c-5 when divided by x-5 leaves no remainder at all.

Given this, we can use knowledge to see that:

(x-5)(x2+5x+55) is equal to x3+30x-c-5.

We can multiply 55 and -5 to get -275, so c is 270.

 

-Random Person :)   

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BTW THIS WAS AN EDIT, THE ANSWER FOR C is 270 NOT -270!!!

 Dec 9, 2019
edited by RandomPerson  Dec 9, 2019
 #2
avatar+106519 
+1

Using sythetic division

 

5   [     1        0             30            - c   ]

                     5             25          275

       __________________________

           1        5            55             5

 

Which implies that

 

275 -  c  = 5

 

c  = 270

 

cool cool cool

 Dec 9, 2019

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