Math Is Fun Forum

chriss

Member

Registered: 2009-02-08

Posts: 4

HELP!!!! with Polynomial

Hello, does anybody knows how to solve this problem:
Given the polynomials A=x^3 +2x -1 and B=x^2-x+3
evaluate them for  x= -2,-1,0,1,2,3 and calculate their product and its coefficients. And its interposition
I need another way on doing this, instead of calculating A and B one by one
(I shouldn't use the simple method ie.  ....).
How can this be done? Thank you.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: HELP!!!! with Polynomial

Do the evaluating first, that might give you some clues.
This table shows the required values:

x   -2    -1   0   1   2   3

A  -13   -4  -1  2   11  32

B   9     5    3  3    5   9

Hmm. No roots, so no easy factors.
Maybe if we know what the answer is, it'll be easier see how to get there.

Doing it the "simple" way gives AB = x^5-x^4+5x^3-3x^2+7x-3.
That's not particularly nice either.
I have no idea how you'd get that any other way.

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Why did the vector cross the road?
It wanted to be normal.