SOLUTION: use synthetic division to find the quotient and remainder (x^4-3x^3+2x-8)/(x-3)

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Question 113769: use synthetic division to find the quotient and remainder
(x^4-3x^3+2x-8)/(x-3)

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Let's simplify this expression using synthetic division


Start with the given expression %28x%5E4+-+3x%5E3+%2B+2x+-+8%29%2F%28x-3%29

First lets find our test zero:

x-3=0 Set the denominator x-3 equal to zero

x=3 Solve for x.

so our test zero is 3


Now set up the synthetic division table by placing the test zero in the upper left corner and placing the coefficients of the numerator to the right of the test zero.(note: remember if a polynomial goes from -3x%5E3 to 2x%5E1 there is a zero coefficient for x%5E2. This is simply because x%5E4+-+3x%5E3+%2B+2x+-+8 really looks like 1x%5E4%2B-3x%5E3%2B0x%5E2%2B2x%5E1%2B-8x%5E0
3|1-302-8
|

Start by bringing down the leading coefficient (it is the coefficient with the highest exponent which is 1)
3|1-302-8
|
1

Multiply 3 by 1 and place the product (which is 3) right underneath the second coefficient (which is -3)
3|1-302-8
|3
1

Add 3 and -3 to get 0. Place the sum right underneath 3.
3|1-302-8
|3
10

Multiply 3 by 0 and place the product (which is 0) right underneath the third coefficient (which is 0)
3|1-302-8
|30
10

Add 0 and 0 to get 0. Place the sum right underneath 0.
3|1-302-8
|30
100

Multiply 3 by 0 and place the product (which is 0) right underneath the fourth coefficient (which is 2)
3|1-302-8
|300
100

Add 0 and 2 to get 2. Place the sum right underneath 0.
3|1-302-8
|300
1002

Multiply 3 by 2 and place the product (which is 6) right underneath the fifth coefficient (which is -8)
3|1-302-8
|3006
1002

Add 6 and -8 to get -2. Place the sum right underneath 6.
3|1-302-8
|3006
1002-2

Since the last column adds to -2, we have a remainder of -2. This means x-3 is not a factor of x%5E4+-+3x%5E3+%2B+2x+-+8
Now lets look at the bottom row of coefficients:

The first 4 coefficients (1,0,0,2) form the quotient

x%5E3+%2B+2

and the last coefficient -2, is the remainder, which is placed over x-3 like this

-2%2F%28x-3%29



Putting this altogether, we get:

x%5E3+%2B+2%2B-2%2F%28x-3%29

So %28x%5E4+-+3x%5E3+%2B+2x+-+8%29%2F%28x-3%29=x%5E3+%2B+2%2B-2%2F%28x-3%29

which looks like this in remainder form:
%28x%5E4+-+3x%5E3+%2B+2x+-+8%29%2F%28x-3%29=x%5E3+%2B+2 remainder -2


You can use this online polynomial division calculator to check your work