# Thread: polynomial division and remainder theorem

1. ## polynomial division and remainder theorem

Hi;

use remainder theorem to find the remainder of (3x^4 - 5x^2 - 20x -8) / (x + 1).

When using remainder theorem I get remainder -33

and with long division I get remainder 10 which I think is the right answer.

Not sure why I'm getting -33 with remainder theorem
What am I missing?

Thanks.

2. ## Re: polynomial division and remainder theorem

The correct answer is 10. Post your working.

3. ## Re: polynomial division and remainder theorem

...

Code:
-1] ... 3 ... 0 ... -5 ... -20 ... -8

.............-3 ....3.......2 ... 18
---------------------------------------

.......3.....-3....-2.....-18 ... 10

4. ## Re: polynomial division and remainder theorem

Originally Posted by anthonye
Hi;

use remainder theorem to find the remainder of (3x^4 - 5x^2 - 20x -8) / (x + 1).

When using remainder theorem I get remainder -33

and with long division I get remainder 10 which I think is the right answer.

Not sure why I'm getting -33 with remainder theorem
What am I missing?

Thanks.
Using the remainder theorem,
$f(-1)$
$= 3(-1)^4 - 5(-1)^2 - 20(-1) - 8$
$= 3 - 5 + 20 - 8$
$= 10$

5. ## Re: polynomial division and remainder theorem

Yeah I got it thank you.