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Find the value of k for which the limit of the piecewise function exists and evaluate the given limit using L'Hôpital's Rule.

Mathematics

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here are the solutions to the limit problems.

  1. We need to find kk such that lim⁡x→2f(x)\lim_{x \to 2} f(x) exists for the piecewise function: f(x)={kx2+1x≤23x−kx>2f(x) = \begin{cases} kx^2 + 1 & x \le 2 \\ 3x - k & x > 2 \end{cases} For the limit to exist at x=2x=2, the left-hand limit must equal the right-hand limit.
  1. Calculate the left-hand limit.

    $$
    \lim_{x \to 2^-} f(x) = \lim_{x \to 2^-} (kx^2 + 1)
    $$
    Substitute $x=2$:
    $$
    k(2)^2 + 1 = 4k + 1
    $$
    
  2. Calculate the right-hand limit.

    $$
    \lim_{x \to 2^+} f(x) = \lim_{x \to 2^+} (3x - k)
    $$
    Substitute $x=2$:
    $$
    3(2) - k = 6 - k
    $$
    
  3. Set the left-hand limit equal to the right-hand limit and solve for kk.

    $$
    4k + 1 = 6 - k
    $$
    $$
    4k + k = 6 - 1
    $$
    $$
    5k = 5
    $$
    $$
    k = 1
    $$
    The value of $k$ is $\boxed{1}$.
    

    7. We need to evaluate the limit: lim⁡x→0ex−x−1x2 \lim_{x \to 0} \frac{e^x - x - 1}{x^2}

  4. Substitute x=0x=0 into the expression.

    $$
    \frac{e^0 - 0 - 1}{0^2} = \frac{1 - 0 - 1}{0} = \frac{0}{0}
    $$
    This is an indeterminate form, so we apply L'Hôpital's Rule.
    
  5. Apply L'Hôpital's Rule by differentiating the numerator and denominator.

    $$
    \lim_{x \to 0} \frac{\frac{d}{dx}(e^x - x - 1)}{\frac{d}{dx}(x^2)} = \lim_{x \to 0} \frac{e^x - 1}{2x}
    $$
    
  6. Substitute x=0x=0 again.

    $$
    \frac{e^0 - 1}{2(0)} = \frac{1 - 1}{0} = \frac{0}{0}
    $$
    This is still an indeterminate form, so we apply L'Hôpital's Rule again.
    
  7. Apply L'Hôpital's Rule a second time.

    $$
    \lim_{x \to 0} \frac{\frac{d}{dx}(e^x - 1)}{\frac{d}{dx}(2x)} = \lim_{x \to 0} \frac{e^x}{2}
    $$
    
  8. Substitute x=0x=0 into the simplified expression.

    $$
    \frac{e^0}{2} = \frac{1}{2}
    $$
    The limit is $\boxed{\frac{1}{2}}$.
    

    8. We need to evaluate the limit: lim⁡x→∞(1+3x)2x \lim_{x \to \infty} \left(1 + \frac{3}{x}\right)^{2x}

  9. Recognize this as a standard limit form.

    The limit is of the form $\lim_{x \to \infty} \left(1 + \frac{a}{x}\right)^{bx} = e^{ab}$.
    
  10. Identify aa and bb from the given limit.

    In this case, $a=3$ and $b=2$.
    
  11. Apply the formula.

    $$
    e^{(3)(2)} = e^6
    $$
    The limit is $\boxed{e^6}$.
    

    9. We need to evaluate the limit: lim⁡x→0x2cos⁡(1x) \lim_{x \to 0} x^2 \cos\left(\frac{1}{x}\right)

  12. Understand the behavior of cos⁡(1x)\cos\left(\frac{1}{x}\right).

    For any $x \ne 0$, the value of $\cos\left(\frac{1}{x}\right)$ is always between $-1$ and 1.
    $$
    -1 \le \cos\left(\frac{1}{x}\right) \le 1
    $$
    
  13. Apply the Squeeze Theorem.

    Multiply the inequality by $x^2$. Since $x^2 \ge 0$, the direction of the inequalities remains the same.
    $$
    -x^2 \le x^2 \cos\left(\frac{1}{x}\right) \le x^2
    $$
    
  14. Evaluate the limits of the bounding functions as x→0x \to 0.

    $$
    \lim_{x \to 0} (-x^2) = -(0)^2 = 0
    $$
    $$
    \lim_{x \to 0} (x^2) = (0)^2 = 0
    $$
    
  15. Conclude using the Squeeze Theorem.

    Since both bounding functions approach 0 as $x \to 0$, the limit of the middle function must also be 0.  
    The limit is $\boxed{0}$.
    

    10. We need to evaluate the limit: lim⁡x→−2∣x+2∣x+2 \lim_{x \to -2} \frac{|x+2|}{x+2}

  16. Define the absolute value function for xx near −2-2.

    $$
    |x+2| = \begin{cases} x+2 & \text{if } x+2 \ge 0 \implies x \ge -2 \\ -(x+2) & \text{if } x+2 < 0 \implies x < -2 \end{cases}
    $$
    
  17. Calculate the left-hand limit.

    As $x \to -2^-$ (meaning $x$ is slightly less than $-2$), $x+2 < 0$, so $|x+2| = -(x+2)$.
    $$
    \lim_{x \to -2^-} \frac{-(x+2)}{x+2} = \lim_{x \to -2^-} (-1) = -1
    $$
    
  18. Calculate the

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