SOLUTION: Dividing Polynomials: synthetic 2x^4 - 10x^2 + 6x - 8 divided by x + 3 please help me if you can

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Question 85753: Dividing Polynomials: synthetic

2x^4 - 10x^2 + 6x - 8 divided by x + 3
please help me if you can

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

Start with the given polynomial %282x%5E4+-+10x%5E2+%2B+6x+-+8%29%2F%28x%2B3%29

First lets find our test zero:

x%2B3=0 Set the denominator x%2B3 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 upperleft corner and placing the coefficients of the numerator to the right of the test zero.(note: remember if a polynomial goes from 2x%5E4 to -10x%5E2 there is a zero coefficient. This is simply because 2x%5E4+-+10x%5E2+%2B+6x+-+8 really looks like 2x%5E4%2B0x%5E3%2B-10x%5E2%2B6x%5E1%2B-8x%5E0
-3|20-106-8

Start by bringing down the leading coefficient (it is the coefficient with the highest exponent which is 2)
-3|20-106-8
2

Multiply -3 by 2 and place the product (which is -6) right underneath 0
-3|20-106-8
-6
2

Add -6 and 0 to get -6. Place the sum right underneath -6.
-3|20-106-8
-6
2-6

Multiply -3 by -6 and place the product (which is 18) right underneath -10
-3|20-106-8
-618
2-6

Add 18 and -10 to get 8. Place the sum right underneath 18.
-3|20-106-8
-618
2-68

Multiply -3 by 8 and place the product (which is -24) right underneath 6
-3|20-106-8
-618-24
2-68

Add -24 and 6 to get -18. Place the sum right underneath -24.
-3|20-106-8
-618-24
2-68-18

Multiply -3 by -18 and place the product (which is 54) right underneath -8
-3|20-106-8
-618-2454
2-68-18

Add 54 and -8 to get 46. Place the sum right underneath 54.
-3|20-106-8
-618-2454
2-68-1846

Since the last column adds to 46, we have a remainder of 46. This means x%2B3 is a not factor of 2x%5E4+-+10x%5E2+%2B+6x+-+8
Now lets look at the bottom row of coefficients:

The first 4 coefficients (2,-6,8,-18) form the quotient

2x%5E3+-+6x%5E2+%2B+8x+-+18

and the last coefficient 46, is the remainder, which is placed over x%2B3 like this

46%2F%28x%2B3%29
Putting this altogether, we get:

2x%5E3+-+6x%5E2+%2B+8x+-+18%2B46%2F%28x%2B3%29

So

which looks like this in remainder form:
%282x%5E4+-+10x%5E2+%2B+6x+-+8%29%2F%28x%2B3%29=2x%5E3+-+6x%5E2+%2B+8x+-+18 remainder 46