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1.3 Dividing polynomials

If the polynomials have (degreef)(degreeg)({\hbox{degree}}\,f)\geq({\hbox{degree}}\,g), then we can use polynomial long division to write

f(x)g(x)=q(x)+r(x)g(x){\frac{f(x)}{g(x)}}=q(x)+{\frac{r(x)}{g(x)}}

where q(x)q(x) is a polynomial and r(x)r(x) is a polynomial with (degreer)<(degreeg)({\hbox{degree}}\,r)<({\hbox{degree}}\,g). (See MATH111, Thm. 7.1.10 for a proof.) It is easy to integrate the polynomial q(x).q(x).

Example.

For f(x)=x6+12x2+39x-44f(x)=x^{6}+12x^{2}+39x-44, g(x)=x3+x2+3x-5g(x)=x^{3}+x^{2}+3x-5 we have 𝑑𝑒𝑔𝑟𝑒𝑒f=6>𝑑𝑒𝑔𝑟𝑒𝑒g=3{\hbox{degree}}\,f=6>{\hbox{degree}}\,g=3. In this case we have

f(x)g(x)=x3-x2-2x+10+3x2-x+6x3+x2+3x-5{\frac{f(x)}{g(x)}}=x^{3}-x^{2}-2x+10+{\frac{3x^{2}-x+6}{x^{3}+x^{2}+3x-5}}