The domain of a rational function should be all real numbers except for when the denominator is equal to 0. To find when the denominator is equal to 0 you simply need to find the zeroes of the denominator... but in this case you can do that through factoring and using the quadratic equation.

So first step is going to be to factor out the GCF, which in this case is x. This gives you the equation. $x(2x^2-x-15)$ . So one of the zeroes is when x=0. Now to find the other two zeroes you can use the quadratic equation which is $x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\\\\$ . So to find the other zeroes you simply plug the values in. a=2, b=-1, c=-15

$x=\frac{-(-1)\pm\sqrt{(-1)^2-4(2)(-15)}}{2(2)}\\\\x=\frac{1\pm\sqrt{1-4(2)(-15)}}{4}\\\\x=\frac{1\pm\sqrt{121)}}{4}\\\\x=\frac{1\pm11}{4}\\\\x=\frac{12}{4}\\x=3\\\\x=\frac{-10}{4}\\x=-\frac{5}{2}$

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2 years ago