3) \( \lim _{x \rightarrow-5} \frac{x^{2}-25}{(x+5)(x-6)} \)
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The Deep Dive
To evaluate the limit \( \lim_{x \rightarrow -5} \frac{x^{2}-25}{(x+5)(x-6)} \), we start by substituting \( x = -5 \). Direct substitution gives us: \[ \frac{(-5)^{2}-25}{((-5)+5)((-5)-6)} = \frac{25 - 25}{0 \cdot (-11)} = \frac{0}{0}, \] which is indeterminate. To resolve this, we can factor the numerator. The expression \( x^{2}-25 \) can be factored as: \[ x^{2}-25 = (x-5)(x+5). \] Thus, the limit can be rewritten as: \[ \lim_{x \rightarrow -5} \frac{(x-5)(x+5)}{(x+5)(x-6)}. \] We can cancel the \( (x+5) \) term (as long as \( x \neq -5 \)): \[ = \lim_{x \rightarrow -5} \frac{x-5}{x-6}. \] Now we substitute \( x = -5 \): \[ = \frac{-5-5}{-5-6} = \frac{-10}{-11} = \frac{10}{11}. \] Thus, the limit is: \[ \boxed{\frac{10}{11}}. \]