rf
HI!!
this looks like it could be hard, but maybe not too hard
so its (x-5) at the bottom
yes
and the asymptote is \(y=x^2-3x\) so when you divide the top by the bottom you should get \(x^2-3x\) with some remainder
lets call the numerator \(p(x)\) so that \[\frac{p(x)}{x-5}=x^2-3x+\frac{R}{x-5}\] or more simply \[p(x)=(x^2-3x)(x-5)+R\]
now we can replace \(x\) by \(-1\) and set the result equal to \(3\) and see if we can solve for \(R\)
you with me so far?
cause we are almost done
yes
ok if we replace \(x\) by \(-1\) in the denominator, we get \(-1-5=-6\)
that means the numerator has to be \(-18\) so that the fraction will be \[-\frac{18}{-6}=3\]
\[p(x)=(x^2-3x)(x-5)+R\] put \(x=-1\) set the result equal to \(-18\) and solve for \(R\)
in other words, solve \[p(-1)=((-1)^2-3(-1))(-1-5)+R=18\] for \(R|)
ooops \[p(-1)=((-1)^2-3(-1))(-1-5)+R=-18\]
there may have been an easier way to do it, but i don't know it you get \[4\times (-6)+R=-18\] or \[-24+R=-18\]
so what is the rational function
we get \(R=6\) right?
yep
that means the numerator is \[p(x)=(x^2-3x)(x-5)+6\]
multiply that out, combine like terms etc, and you answer will be that polynomial over \(x-5\)
if you do it correctly you will get \[\frac{x^3-8 x^2+15 x+6}{x-5}\]
Join our real-time social learning platform and learn together with your friends!