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Let

f(x)={[log(3x)," for "0 < x < 3],[(4-x)log(9)," for "x >= 3]:}
Is 
f continuous at 
x=3 ?
Choose 1 answer:
(A) Yes
(B) No

Let\newline\( f(x)=\left\{\begin{array}{ll}\log (3 x) & \text { for } 0

Full solution

Q. Let\newlinef(x)={log(3x) for 0<x<3(4x)log(9) for x3 f(x)=\left\{\begin{array}{ll}\log (3 x) & \text { for } 0<x<3 \\ (4-x) \log (9) & \text { for } x \geq 3\end{array}\right. \newlineIs f f continuous at x=3 x=3 ?\newlineChoose 11 answer:\newline(A) Yes\newline(B) No
  1. Check f(3)f(3) is defined: To determine if the function f(x)f(x) is continuous at x=3x=3, we need to check if the following conditions are met:\newline11. f(3)f(3) is defined.\newline22. The limit of f(x)f(x) as xx approaches 33 from the left (limx3f(x)\lim_{x\to3^-} f(x)) exists.\newline33. The limit of f(x)f(x) as xx approaches 33 from the right (f(x)f(x)11) exists.\newline44. The two one-sided limits are equal to each other and to f(3)f(3).\newlineFirst, we will find f(3)f(3) using the definition of the function for f(x)f(x)44.
  2. Find f(3)f(3): Substitute x=3x = 3 into the second part of the function definition, (4x)log(9)(4-x)\log(9), to find f(3)f(3).
    f(3)=(43)log(9)=log(9)=log(32)=2log(3)f(3) = (4-3)\log(9) = \log(9) = \log(3^2) = 2\log(3).
  3. Find the limit from the left: Now, we need to find the limit of f(x)f(x) as xx approaches 33 from the left. This means we will use the first part of the function definition, log(3x)\log(3x), and take the limit as xx approaches 33.limx3f(x)=limx3log(3x)=log(33)=log(9)=2log(3)\lim_{x\to 3^-} f(x) = \lim_{x\to 3^-} \log(3x) = \log(3\cdot 3) = \log(9) = 2\log(3).
  4. Find the limit from the right: Next, we need to find the limit of f(x)f(x) as xx approaches 33 from the right. This means we will use the second part of the function definition, (4x)log(9)(4-x)\log(9), and take the limit as xx approaches 33.limx3+f(x)=limx3+(4x)log(9)=(43)log(9)=log(9)=2log(3)\lim_{x\to 3^+} f(x) = \lim_{x\to 3^+} (4-x)\log(9) = (4-3)\log(9) = \log(9) = 2\log(3).
  5. Compare the limits and f(3)f(3): We have found that f(3)=2log(3)f(3) = 2\log(3), the limit from the left is 2log(3)2\log(3), and the limit from the right is also 2log(3)2\log(3). Since all three values are equal, the function f(x)f(x) is continuous at x=3x=3.

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