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Polynomial Long Division

  1. Aug 30, 2009 #1
    I am trying to solve:

    [tex]\frac{x^6+6x^3-2x^5-7x^2-4x+6}{x^4-3x^2+2}[/tex]

    Using the polynomial long division algorithm.

    I order first the terms of the divident, and leave one blank space between -2x^5 and +6x^3

    My problem is, I first put x^2 to the quotient, so I get x^4 * x^2 = x^6, but then I multiply x^2 * -3x^2 = -3x^4, which can't be subtracted with -2x^5.

    I have tried playing around but with no success.

    Thanks
     
  2. jcsd
  3. Aug 30, 2009 #2
    You also need to leave blank spaces in your divisor. Better yet, where there should be blank spaces, put the missing term with a coefficient of 0. In your divisor, put 0x3. Multiply that by x2 and you get 0x5 which should be easy to subtract from -2x5. Try doing that with all missing terms in the dividend and divisor because it can be easy to miss something with all those terms.
     
  4. Aug 30, 2009 #3

    symbolipoint

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    Your dividend takes the form as x^6 -2*x^5 +0*x^4 +6*x^3 -7*x^2 -4x +6
    Restating your divisor as x^4 +0*x^3 -3*x^2 +0*x +2

    Notice every degree of x must be shown. This is like keeping "place value" in "integers" were those to be divided, but now we are keeping track of powers of x, not powers of 10.

    Your first partial division was (x^6)/(x^4)=x^2, this was good. Now, how much complete divisor do you subtract? Find this by performing multiplication:
    (x^2)*(x^4 +0*x^3 -3*x^2 +0*x +2)=x^6 +0*x^5 -3*x^4 +0*x^3 +2*x^2

    Now you write x^6 +0*x^5 -3*x^4 +0*x^3 +2*x^2 in proper alignment under the dividend and perform your first subtraction. Now, continue from here.
     
  5. Aug 30, 2009 #4
    Thank you, much easier with putting zeros.

    I also noticed that I messed up a lot doing this: 0x^4 - (-3x^4) = +3x^4, I forgot to change the sign many times.

    Your help is very much appreciated.
     
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