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Symmetry classification

Consider the function w(x)=x3x2−9w(x) = \dfrac{x^3}{x^2 - 9}.

Determine whether w(x)=x3x2−9w(x) = \dfrac{x^3}{x^2-9} is even, odd, or neither. State your conclusion.

Hint

Compute w(−x)w(-x) and compare it to w(x)w(x) and to −w(x)-w(x).

Step-by-step solution

Substitute −x-x for xx: w(−x)=(−x)3(−x)2−9=−x3x2−9w(-x) = \dfrac{(-x)^3}{(-x)^2-9} = \dfrac{-x^3}{x^2-9}.

This equals −w(x)-w(x), so the function satisfies w(−x)=−w(x)w(-x) = -w(x), meaning ww is odd (symmetric about the origin).

Vertical asymptotes

Find all vertical asymptotes of w(x)=x3x2−9w(x) = \dfrac{x^3}{x^2-9}.

Hint

Find where the denominator is zero and check that the numerator is nonzero there.

Step-by-step solution

Set the denominator equal to zero: x2−9=0x^2 - 9 = 0, giving x=3x = 3 and x=−3x = -3.

At both values the numerator x3x^3 is nonzero (27 and -27 respectively), so both are vertical asymptotes: x=3x=3 and x=−3x=-3.

Slant asymptote via polynomial division

Perform polynomial long division on w(x)=x3x2−9w(x) = \dfrac{x^3}{x^2-9} to find its slant (oblique) asymptote.

Hint

Divide x3x^3 by x2−9x^2-9; the quotient (ignoring the remainder term) gives the slant asymptote line.

Step-by-step solution

Dividing x3x^3 by x2−9x^2 - 9: x3=x⋅(x2−9)+9xx^3 = x\cdot(x^2-9) + 9x, so w(x)=x+9xx2−9w(x) = x + \dfrac{9x}{x^2-9}.

As x→±∞x \to \pm\infty, the remainder term 9xx2−9→0\dfrac{9x}{x^2-9} \to 0, so the graph approaches the line y=xy = x. This is the slant asymptote.

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