Subjects algebra

Asymptotes Holes

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1. **State the problem:** We are given the function $$f(x) = \frac{x^3 + 5x^2 - 6x}{x^2 - 1}$$ and need to find: (i) The vertical asymptote(s) and/or hole(s) of the graph. (ii) The horizontal or oblique asymptote(s), if any. 2. **Recall important rules:** - Vertical asymptotes occur where the denominator is zero but the numerator is not zero at those points. - Holes occur where both numerator and denominator are zero at the same point (common factors). - Horizontal asymptotes depend on the degrees of numerator and denominator polynomials. - Oblique (slant) asymptotes occur if the degree of numerator is exactly one more than denominator. 3. **Find vertical asymptotes and holes:** - Factor numerator and denominator: $$x^3 + 5x^2 - 6x = x(x^2 + 5x - 6) = x(x+6)(x-1)$$ $$x^2 - 1 = (x-1)(x+1)$$ - Simplify the function: $$f(x) = \frac{x(x+6)(x-1)}{(x-1)(x+1)} = \frac{x(x+6)\cancel{(x-1)}}{\cancel{(x-1)}(x+1)} = \frac{x(x+6)}{x+1}, \quad x \neq 1$$ - The factor \((x-1)\) cancels, so at \(x=1\) there is a hole. - The denominator is zero at \(x = -1\) and numerator is not zero there, so vertical asymptote at \(x = -1\). 4. **Find horizontal or oblique asymptotes:** - Degree numerator after simplification: 2 (since numerator is \(x(x+6) = x^2 + 6x\)) - Degree denominator: 1 - Since numerator degree (2) is exactly one more than denominator degree (1), there is an oblique asymptote. - Perform polynomial division of numerator by denominator: $$\frac{x^2 + 6x}{x+1}$$ Divide: - \(x^2 \div x = x\), multiply \(x(x+1) = x^2 + x\) - Subtract: \((x^2 + 6x) - (x^2 + x) = 5x\) - Divide: \(5x \div x = 5\), multiply \(5(x+1) = 5x + 5\) - Subtract: \(5x - (5x + 5) = -5\) - Remainder \(-5\) over divisor \(x+1\) - So quotient is \(x + 5\) and remainder \(-5/(x+1)\) - Oblique asymptote is the line: $$y = x + 5$$ **Final answers:** - Vertical asymptote at \(x = -1\) - Hole at \(x = 1\) - Oblique asymptote: \(y = x + 5\)