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Let f (x) =(2 |x| -1)/(x-3) Range of f...

Let `f (x) =(2 |x| -1)/(x-3)`
Range of `f (x):`

A

`R- {3}`

B

`(-oo, (1)/(3) ] uu (2,oo)`

C

`(-2, (1)/(3)]` uu (2,oo)`

D

R

Text Solution

AI Generated Solution

The correct Answer is:
To find the range of the function \( f(x) = \frac{2|x| - 1}{x - 3} \), we will analyze the function by considering two cases based on the absolute value of \( x \). ### Step 1: Case 1 - When \( x \geq 0 \) For \( x \geq 0 \), we have \( |x| = x \). Thus, the function becomes: \[ f(x) = \frac{2x - 1}{x - 3} \] Let \( y = f(x) \): \[ y = \frac{2x - 1}{x - 3} \] Cross-multiplying gives: \[ yx - 3y = 2x - 1 \] Rearranging this, we get: \[ yx - 2x = 3y - 1 \] Factoring out \( x \): \[ x(y - 2) = 3y - 1 \] Thus, \[ x = \frac{3y - 1}{y - 2} \] Since \( x \geq 0 \), we require: \[ \frac{3y - 1}{y - 2} \geq 0 \] ### Step 2: Solve the Inequality To solve \( \frac{3y - 1}{y - 2} \geq 0 \), we find the critical points by setting the numerator and denominator to zero: - \( 3y - 1 = 0 \) gives \( y = \frac{1}{3} \) - \( y - 2 = 0 \) gives \( y = 2 \) Now we analyze the sign of the expression on the number line: - The critical points divide the number line into intervals: \( (-\infty, \frac{1}{3}) \), \( (\frac{1}{3}, 2) \), and \( (2, \infty) \). Testing each interval: 1. For \( y < \frac{1}{3} \): Choose \( y = 0 \) → \( \frac{3(0) - 1}{0 - 2} = \frac{-1}{-2} > 0 \) (positive) 2. For \( \frac{1}{3} < y < 2 \): Choose \( y = 1 \) → \( \frac{3(1) - 1}{1 - 2} = \frac{2}{-1} < 0 \) (negative) 3. For \( y > 2 \): Choose \( y = 3 \) → \( \frac{3(3) - 1}{3 - 2} = \frac{8}{1} > 0 \) (positive) Thus, the solution to the inequality is: \[ y \in (-\infty, \frac{1}{3}] \cup (2, \infty) \] ### Step 3: Case 2 - When \( x < 0 \) For \( x < 0 \), we have \( |x| = -x \). Thus, the function becomes: \[ f(x) = \frac{-2x - 1}{x - 3} \] Let \( y = f(x) \): \[ y = \frac{-2x - 1}{x - 3} \] Cross-multiplying gives: \[ yx - 3y = -2x - 1 \] Rearranging this, we get: \[ yx + 2x = 3y - 1 \] Factoring out \( x \): \[ x(y + 2) = 3y - 1 \] Thus, \[ x = \frac{3y - 1}{y + 2} \] Since \( x < 0 \), we require: \[ \frac{3y - 1}{y + 2} < 0 \] ### Step 4: Solve the Inequality To solve \( \frac{3y - 1}{y + 2} < 0 \), we find the critical points: - \( 3y - 1 = 0 \) gives \( y = \frac{1}{3} \) - \( y + 2 = 0 \) gives \( y = -2 \) Now we analyze the sign of the expression on the number line: - The critical points divide the number line into intervals: \( (-\infty, -2) \), \( (-2, \frac{1}{3}) \), and \( (\frac{1}{3}, \infty) \). Testing each interval: 1. For \( y < -2 \): Choose \( y = -3 \) → \( \frac{3(-3) - 1}{-3 + 2} = \frac{-10}{-1} > 0 \) (positive) 2. For \( -2 < y < \frac{1}{3} \): Choose \( y = 0 \) → \( \frac{3(0) - 1}{0 + 2} = \frac{-1}{2} < 0 \) (negative) 3. For \( y > \frac{1}{3} \): Choose \( y = 1 \) → \( \frac{3(1) - 1}{1 + 2} = \frac{2}{3} > 0 \) (positive) Thus, the solution to the inequality is: \[ y \in (-2, \frac{1}{3}) \] ### Step 5: Combine the Results Now we combine the results from both cases: 1. From Case 1: \( y \in (-\infty, \frac{1}{3}] \cup (2, \infty) \) 2. From Case 2: \( y \in (-2, \frac{1}{3}) \) Combining these intervals, we get: \[ \text{Range of } f(x) = (-\infty, \frac{1}{3}) \cup (2, \infty) \] ### Final Answer The range of the function \( f(x) \) is: \[ (-\infty, \frac{1}{3}) \cup (2, \infty) \]
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