SOLUTION: Divide: 5x^3-5x+1 by x-3 I tried factoring out the 5 and ended up with 5(x^2-x-3)+x as the answer Am I anywhere close?????

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Question 117090: Divide: 5x^3-5x+1 by x-3
I tried factoring out the 5 and ended up with 5(x^2-x-3)+x as the answer
Am I anywhere close?????

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 %285x%5E3+-+5x+%2B+1%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 5x%5E3 to -5x%5E1 there is a zero coefficient for x%5E2. This is simply because 5x%5E3+-+5x+%2B+1 really looks like 5x%5E3%2B0x%5E2%2B-5x%5E1%2B1x%5E0
3|50-51
|

Start by bringing down the leading coefficient (it is the coefficient with the highest exponent which is 5)
3|50-51
|
5

Multiply 3 by 5 and place the product (which is 15) right underneath the second coefficient (which is 0)
3|50-51
|15
5

Add 15 and 0 to get 15. Place the sum right underneath 15.
3|50-51
|15
515

Multiply 3 by 15 and place the product (which is 45) right underneath the third coefficient (which is -5)
3|50-51
|1545
515

Add 45 and -5 to get 40. Place the sum right underneath 45.
3|50-51
|1545
51540

Multiply 3 by 40 and place the product (which is 120) right underneath the fourth coefficient (which is 1)
3|50-51
|1545120
51540

Add 120 and 1 to get 121. Place the sum right underneath 120.
3|50-51
|1545120
51540121

Since the last column adds to 121, we have a remainder of 121. This means x-3 is not a factor of 5x%5E3+-+5x+%2B+1
Now lets look at the bottom row of coefficients:

The first 3 coefficients (5,15,40) form the quotient

5x%5E2+%2B+15x+%2B+40

and the last coefficient 121, is the remainder, which is placed over x-3 like this

121%2F%28x-3%29



Putting this altogether, we get:

5x%5E2+%2B+15x+%2B+40%2B121%2F%28x-3%29

So %285x%5E3+-+5x+%2B+1%29%2F%28x-3%29=5x%5E2+%2B+15x+%2B+40%2B121%2F%28x-3%29

which looks like this in remainder form:
%285x%5E3+-+5x+%2B+1%29%2F%28x-3%29=5x%5E2+%2B+15x+%2B+40 remainder 121


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