15x
____
(x^4 + 1)^(1/4)
i dont know what to do, do i divide each term by x^4 ? its what i did and i got the wrong answer unless i did it wrong
To get a clearer relationship between numerator and denominator,
write the x part of the numerator to the power of 0.25
$\displaystyle \frac{15\left(x^4\right)^{\frac{1}{4}}}{\left(x^4+ 1\right)^{\frac{1}{4}}}$
$\displaystyle =15\left(\frac{x^4}{x^4+1}\right)^{\frac{1}{4}}$
now the limit as x approaches infinity is clearer.
Refer back to your original expression for the polarity as x goes to plus or minus infinity.