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if p in (0,1//e)then the number of the d...

if `p in (0,1//e)`then the number of the distinct roots of the equation `|ln x| - px =0` is :

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To solve the equation \( |\ln x| - px = 0 \) for \( p \in (0, \frac{1}{e}) \), we will analyze the equation step by step. ### Step 1: Rewrite the equation The equation can be rewritten as: \[ |\ln x| = px \] This means we have two cases to consider based on the definition of the absolute value. ### Step 2: Consider the cases for \( |\ln x| \) 1. **Case 1**: \( \ln x = px \) 2. **Case 2**: \( -\ln x = px \) or equivalently \( \ln x = -px \) ### Step 3: Analyze Case 1: \( \ln x = px \) To find the roots of \( \ln x = px \), we can rewrite it as: \[ \ln x - px = 0 \] Define the function: \[ f_1(x) = \ln x - px \] Now, we will find the derivative: \[ f_1'(x) = \frac{1}{x} - p \] Setting the derivative to zero to find critical points: \[ \frac{1}{x} - p = 0 \implies x = \frac{1}{p} \] Now, we need to check if this critical point is within the valid range of \( x \) (i.e., \( x > 0 \)): - Since \( p < \frac{1}{e} \), \( \frac{1}{p} > e \). Thus, \( x = \frac{1}{p} \) is valid. Next, we evaluate \( f_1(x) \) at the boundaries and at the critical point: - As \( x \to 0^+ \), \( f_1(x) \to -\infty \). - At \( x = \frac{1}{p} \): \[ f_1\left(\frac{1}{p}\right) = \ln\left(\frac{1}{p}\right) - p\left(\frac{1}{p}\right) = -\ln p - 1 \] Since \( p \in (0, \frac{1}{e}) \), \( -\ln p > 0 \) and thus \( f_1\left(\frac{1}{p}\right) < 0 \). - As \( x \to \infty \), \( f_1(x) \to \infty \). By the Intermediate Value Theorem, since \( f_1(x) \) is continuous, there are two roots for \( \ln x = px \). ### Step 4: Analyze Case 2: \( -\ln x = px \) For this case, we rewrite it as: \[ \ln x = -px \] Define the function: \[ f_2(x) = \ln x + px \] Finding the derivative: \[ f_2'(x) = \frac{1}{x} + p \] Since \( p > 0 \) and \( \frac{1}{x} > 0 \) for \( x > 0 \), \( f_2'(x) > 0 \) for all \( x > 0 \). This means \( f_2(x) \) is strictly increasing. Now, we evaluate \( f_2(x) \): - As \( x \to 0^+ \), \( f_2(x) \to -\infty \). - As \( x \to \infty \), \( f_2(x) \to \infty \). Since \( f_2(x) \) is continuous and strictly increasing, there is exactly one root for \( \ln x = -px \). ### Step 5: Combine the results From both cases, we have: - Case 1: Two distinct roots from \( \ln x = px \). - Case 2: One distinct root from \( \ln x = -px \). Thus, the total number of distinct roots of the equation \( |\ln x| - px = 0 \) is: \[ \text{Total roots} = 2 + 1 = 3 \] ### Final Answer The number of distinct roots of the equation \( |\ln x| - px = 0 \) is **3**.
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