Partial Solutions


  1. There is no solution provided for this question.
    1.  \[\begin{align*} \lim_{x \rightarrow 5} ~ (2x + 3) &= \lim_{x \to 5} ~ 2x + \lim_{x \to 5} ~ 3 & \text{property 3} \\ &= 2 \lim_{x \rightarrow 5} ~ x + \lim_{x \rightarrow 5} ~ 3 & \text{property 4} \\ &= 2(5) + 3 & \text{properties 2 and 1} \\ &= 13 \end{align*}\]
    2.  \[\begin{align*} \lim_{x \rightarrow 2} ~ (-x^2 + 3x - 2) &= \lim_{x \to 2} ~ (-x^2) + \lim_{x \to 2} ~ (3x) - \lim_{x \to 2}~2 & \text{property 3} \\ &= -\left( \lim_{x \rightarrow 2} ~ x \right)^2 + 3\lim_{x \rightarrow 2} ~ x - \lim_{x \rightarrow 2} ~ 2 & \text{properties 4 and 7}\\ &= -\left( 2 \right)^2 + 3(2) - 2 & \text{properties 2 and 1} \\ &= 0 \end{align*}\]
    3.  \[\begin{align*} \lim_{t \rightarrow -1} ~ 5(t - 2)(t - 3) &= 5 \left( \lim_{t \rightarrow -1} ~ (t - 2) \right) \left( \lim_{t \rightarrow -1} ~ (t - 3) \right) & \text{properties 4 and 5} \\ &= 5 \left( \lim_{t \rightarrow -1} ~ t - \lim_{t \rightarrow -1} 2 \right) \left( \lim_{t \rightarrow -1} ~ t - \lim_{t \rightarrow -1} ~ 3 \right) & \text{property 3} \\ &= 5 \left( -1 - 2 \right) \left( -1 - 3 \right) & \text{properties 2 and 1} \\ &= 60 \end{align*}\]
    4.  \[\begin{align*} \lim_{x \rightarrow 3} ~ \dfrac{x + 3}{x - 2} &= \dfrac{ \displaystyle \lim_{x \rightarrow 3} ~ (x + 3)}{ \displaystyle \lim_{x \rightarrow 3} ~ (x - 2)} & \text{property 6} \\ &= \dfrac{ \displaystyle \lim_{x \rightarrow 3} ~ x + \lim_{x \rightarrow 3} 3}{ \displaystyle \lim_{x \rightarrow 3} ~ x - \lim_{x \rightarrow 3} 2} & \text{property 3} \\ &= \dfrac{3 + 3}{3 - 2} & \text{properties 1 and 2} \\ &= \dfrac{6}{1} \\ &= 6 \end{align*}\]
    5.  \[\begin{align*} \lim_{x \rightarrow 0} ~ 2(2x - 1)^3 &= 2 \left( 2 \lim_{x \rightarrow 0} ~ x - \lim_{x \rightarrow 0} ~ 1 \right)^3 & \text{properties 4, 3, and 7} \\ &= 2(2(0) - 1)^3 & \text{properties 1 and 2} \\ &= -2 \end{align*}\]
    6.  \[\begin{align*} \lim_{x \rightarrow -3} ~ (5 - x)^{\frac{4}{3}} &= \left( \lim_{x \rightarrow -3} 5 - \lim_{x \rightarrow -3} x \right)^{\frac{4}{3}} & \text{properties 3 and 7} \\ &= (5 - (-3))^{\frac{4}{3}} & \text{properties 1 and 2} \\ &= 16 \end{align*}\]
  2. There is no solution provided for this question.
  3.  \[\begin{align*} \lim_{x \rightarrow 1} \dfrac{[f(x)]^3 + [g(x)]^2}{5 - 2g(x)} &= \dfrac{ \left( \displaystyle \lim_{x \rightarrow 1} ~ f(x) \right)^3 + \left( \displaystyle \lim_{x \rightarrow 1} ~ g(x) \right)^2}{\displaystyle \lim_{x \rightarrow 1} ~ 5 - 2 \lim_{x \rightarrow 1} g(x)} \\ &= \dfrac{(-2)^3 + (3)^2}{5 - 2(3)} \\ &= -1 \end{align*}\]
  4. There is no solution provided for this question.
  5. Line f through (a, f(a)), (b, 6); line g through (a, f(a)), (b, 2)

    The points \( (a, 0) \) and \( (b, a) \) lie on the line \( y = f(x) \) and so an equation to the line is

    \[ f(x) = \dfrac{6}{b - a} (x - a) \]

    Similarly, an equation for the line \( y = g(x) \) is

    \[ g(x) = \dfrac{2}{b - a}(x - a) \]

    If \( x \neq a \), then \( g(x) \neq 0 \) and \( \dfrac{f(x)}{g(x)} = 3 \). Therefore, \( \displaystyle\lim_{x \to a} ~ \dfrac{f(x)}{g(x)} = 3 \).

    This limit can also be evaluated using similar triangles.

     
  6. There is no solution provided for this question.
  7. There are many possible solutions to this question. One possible function is\[ f(x) = \begin{cases} 1 &\text{if } x \gt 0 \\ -1 &\text{if } x \leq 0 \end{cases} \] Observe that \( f(x)^2 = 1 \) for all \( x \in \mathbb{R} \). Then \( \displaystyle \lim_{x \rightarrow 0} ~ [f(x)]^2 = 1 \). However, by definition of \( f(x) \),\[ \displaystyle \lim_{x \rightarrow 0^-} ~ f(x) = -1 \neq 1 = \lim_{x \rightarrow 0^+} ~ f(x) \] so \( \displaystyle \lim_{x \rightarrow 0} ~ f(x) \) does not exist. Piecewise function; y=-1 for x<=0, y=1 for x>0