Subjects calculus

Limit Rational Function B99Df5

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Question: 1) $\lim_{x\to -5}\frac{x^3+5x^2+x+5}{x^2+12x+35}$ 2) Graph/shape: none visible; math expression is centered. position_hint = center
1. **State the problem:** Find the limit $$\lim_{x\to -5}\frac{x^3+5x^2+x+5}{x^2+12x+35}$$ 2. **Recall the formula and rules:** To find limits involving rational functions, if direct substitution leads to an indeterminate form like $\frac{0}{0}$, we try to factor numerator and denominator and simplify. 3. **Evaluate direct substitution:** Substitute $x = -5$: Numerator: $(-5)^3 + 5(-5)^2 + (-5) + 5 = -125 + 125 - 5 + 5 = 0$ Denominator: $(-5)^2 + 12(-5) + 35 = 25 - 60 + 35 = 0$ So direct substitution gives $\frac{0}{0}$, an indeterminate form. 4. **Factor numerator and denominator:** Denominator: $$x^2 + 12x + 35 = (x + 5)(x + 7)$$ Numerator: Group terms: $$x^3 + 5x^2 + x + 5 = (x^3 + 5x^2) + (x + 5) = x^2(x + 5) + 1(x + 5) = (x + 5)(x^2 + 1)$$ 5. **Simplify the expression:** $$\frac{(x + 5)(x^2 + 1)}{(x + 5)(x + 7)}$$ Cancel the common factor $x + 5$: $$\frac{\cancel{(x + 5)}(x^2 + 1)}{\cancel{(x + 5)}(x + 7)} = \frac{x^2 + 1}{x + 7}$$ 6. **Evaluate the limit of the simplified expression:** Substitute $x = -5$: $$\frac{(-5)^2 + 1}{-5 + 7} = \frac{25 + 1}{2} = \frac{26}{2} = 13$$ **Final answer:** $$\lim_{x\to -5}\frac{x^3+5x^2+x+5}{x^2+12x+35} = 13$$