SOLUTION: Divide: (x^3-2x^2+8) / (x+2)

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Divide: (x^3-2x^2+8) / (x+2)      Log On


   



Question 200829: Divide: (x^3-2x^2+8) / (x+2)
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%5E3+-+2x%5E2+%2B+8%29%2F%28x%2B2%29

First lets find our test zero:

x%2B2=0 Set the denominator x%2B2 equal to zero

x=-2 Solve for x.

so our test zero is -2


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 -2x%5E2 to 8x%5E0 there is a zero coefficient for x%5E1. This is simply because x%5E3+-+2x%5E2+%2B+8 really looks like 1x%5E3%2B-2x%5E2%2B0x%5E1%2B8x%5E0
-2|1-208
|

Start by bringing down the leading coefficient (it is the coefficient with the highest exponent which is 1)
-2|1-208
|
1

Multiply -2 by 1 and place the product (which is -2) right underneath the second coefficient (which is -2)
-2|1-208
|-2
1

Add -2 and -2 to get -4. Place the sum right underneath -2.
-2|1-208
|-2
1-4

Multiply -2 by -4 and place the product (which is 8) right underneath the third coefficient (which is 0)
-2|1-208
|-28
1-4

Add 8 and 0 to get 8. Place the sum right underneath 8.
-2|1-208
|-28
1-48

Multiply -2 by 8 and place the product (which is -16) right underneath the fourth coefficient (which is 8)
-2|1-208
|-28-16
1-48

Add -16 and 8 to get -8. Place the sum right underneath -16.
-2|1-208
|-28-16
1-48-8

Since the last column adds to -8, we have a remainder of -8. This means x%2B2 is not a factor of x%5E3+-+2x%5E2+%2B+8
Now lets look at the bottom row of coefficients:

The first 3 coefficients (1,-4,8) form the quotient

x%5E2+-+4x+%2B+8

and the last coefficient -8, is the remainder, which is placed over x%2B2 like this

-8%2F%28x%2B2%29



Putting this altogether, we get:

x%5E2+-+4x+%2B+8%2B-8%2F%28x%2B2%29

So %28x%5E3+-+2x%5E2+%2B+8%29%2F%28x%2B2%29=x%5E2+-+4x+%2B+8%2B-8%2F%28x%2B2%29

which looks like this in remainder form:

%28x%5E3+-+2x%5E2+%2B+8%29%2F%28x%2B2%29=x%5E2+-+4x+%2B+8 remainder -8