Tuesday, October 13, 2015

Calculus and Its Applications, Chapter 1, 1.2, Section 1.2, Problem 14

Determine the $\displaystyle \lim_{x \to 5} (x^2 - 6x + 9) $ by using the Theorem on Limits of Rational Functions.
When necessary, state that the limit does not exist.


$
\begin{equation}
\begin{aligned}
\lim_{x \to 5} (x^2 - 6x + 9) &= \lim_{x \to 5} x^2 - \lim_{x \to 5} 6x + \lim_{x \to 5} 9
&& \text{The limit of a difference is the difference of the limits and the limit of a sum is the sum of the limits}\\
\\
&= \left( \lim_{x \to 5} x\right)^2 - \lim_{x \to 5} 6x + \lim_{x \to 5} 9
&& \text{The limit of a power is the power of the limit}\\
\\
&= \left( \lim_{x \to 5}x \right)^2 - 6 \cdot \lim_{x \to 5} x + \lim_{x \to 5} 9
&& \text{The limit of a constant times a function is the constant times the limit}\\
\\
&= \left( \lim_{x \to 5}x \right)^2 - 6 \cdot \lim_{x \to 5} x + 9
&& \text{The limit of a constant is the constant}\\
\\
&= (2)^2 - 6 \cdot 2 + 9
&& \text{Substitute 2}\\
\\
&= 4 - 12 + 9\\
\\
&= 1
\end{aligned}
\end{equation}
$

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