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Question 4.c asks to find the values of k for which the function g(x) is continuous at x=2.

Computer Science

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Answer

k=12 and k=−1k = \frac{1}{2} \text{ and } k = -1

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Okay, let's solve question 4.c.

c asks to find the values of kk for which the function g(x)g(x) is continuous at x=2x=2.
The function is defined as:

g(x)={k2x2for x≤2(1−k)xfor x>2g(x) = \begin{cases} k^2 x^2 & \text{for } x \le 2 \\ (1-k)x & \text{for } x > 2 \end{cases}

For a function to be continuous at a point x=cx=c, the following conditions must be met:

  1. g(c)g(c) must be defined.
  2. lim⁡x→c−g(x)\lim_{x \to c^-} g(x) must exist.
  3. lim⁡x→c+g(x)\lim_{x \to c^+} g(x) must exist.
  4. lim⁡x→c−g(x)=lim⁡x→c+g(x)=g(c)\lim_{x \to c^-} g(x) = \lim_{x \to c^+} g(x) = g(c).

Here, c=2c=2.

  1. Determine g(2)g(2).

    For x≤2x \le 2, g(x)=k2x2g(x) = k^2 x^2.
    Substituting x=2x=2:

    g(2)=k2(2)2=4k2g(2) = k^2 (2)^2 = 4k^2

    The function is defined at x=2x=2.

  2. Evaluate the left-hand limit lim⁡x→2−g(x)\lim_{x \to 2^-} g(x).

    For x<2x < 2, g(x)=k2x2g(x) = k^2 x^2.

    lim⁡x→2−g(x)=lim⁡x→2−k2x2=k2(2)2=4k2\lim_{x \to 2^-} g(x) = \lim_{x \to 2^-} k^2 x^2 = k^2 (2)^2 = 4k^2
  3. Evaluate the right-hand limit lim⁡x→2+g(x)\lim_{x \to 2^+} g(x).

    For x>2x > 2, g(x)=(1−k)xg(x) = (1-k)x.

    lim⁡x→2+g(x)=lim⁡x→2+(1−k)x=(1−k)(2)=2−2k\lim_{x \to 2^+} g(x) = \lim_{x \to 2^+} (1-k)x = (1-k)(2) = 2 - 2k
  4. Set the left-hand limit, right-hand limit, and g(2)g(2) equal for continuity.

    For g(x)g(x) to be continuous at x=2x=2, we must have:

    lim⁡x→2−g(x)=lim⁡x→2+g(x)=g(2)\lim_{x \to 2^-} g(x) = \lim_{x \to 2^+} g(x) = g(2)

    So, we set the expressions from Step 1, 2, and 3 equal to each other:

    4k2=2−2k4k^2 = 2 - 2k

    Rearrange the equation into a standard quadratic form ax2+bx+c=0ax^2 + bx + c = 0:

    4k2+2k−2=04k^2 + 2k - 2 = 0

    Divide the entire equation by 2 to simplify:

    2k2+k−1=02k^2 + k - 1 = 0

    Factor the quadratic equation:

    2k2+2k−k−1=02k^2 + 2k - k - 1 = 0 2k(k+1)−1(k+1)=02k(k+1) - 1(k+1) = 0 (2k−1)(k+1)=0(2k-1)(k+1) = 0

    This gives two possible values for kk:

    2k−1=0  ⟹  2k=1  ⟹  k=122k-1 = 0 \implies 2k = 1 \implies k = \frac{1}{2} k+1=0  ⟹  k=−1k+1 = 0 \implies k = -1

    The values of kk for which g(x)g(x) is continuous at x=2x=2 are k=12 and k=−1\boxed{k = \frac{1}{2} \text{ and } k = -1}.

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