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A function f(x) having the following pr...

A function f(x) having the following properties,
(i) f(x) is continuous except at x=3
(ii) f(x) is differentiable except at x=-2 and x=3
(iii) `f(0) =0 lim_(x to 3) f(x) to - oo lim_(x to oo) f(x) =3 , lim_(x to oo) f(x)=0`
(iv) `f'(x) gt 0 AA in (-oo, -2) uu (3,oo) " and " f'(x) le 0 AA x in (-2,3)`
(v) `f''(x) gt 0 AA x in (-oo,-2) uu (-2,0)" and "f''(x) lt 0 AA x in (0,3) uu(3,oo)`
Then answer the following questions
Find the Maximum possible number of solutions of `f(x)=|x|`

Text Solution

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The correct Answer is:
To find the maximum possible number of solutions for the equation \( f(x) = |x| \), we will analyze the properties of the function \( f(x) \) step by step. ### Step 1: Analyzing the Properties of \( f(x) \) 1. **Continuity**: The function \( f(x) \) is continuous except at \( x = 3 \). 2. **Differentiability**: The function \( f(x) \) is differentiable except at \( x = -2 \) and \( x = 3 \). 3. **Function Values**: - \( f(0) = 0 \) - \( \lim_{x \to 3} f(x) = -\infty \) - \( \lim_{x \to -\infty} f(x) = 3 \) - \( \lim_{x \to \infty} f(x) = 0 \) 4. **First Derivative**: - \( f'(x) > 0 \) in the intervals \( (-\infty, -2) \) and \( (3, \infty) \) (function is increasing). - \( f'(x) \leq 0 \) in the interval \( (-2, 3) \) (function is decreasing). 5. **Second Derivative**: - \( f''(x) > 0 \) in the intervals \( (-\infty, -2) \) and \( (-2, 0) \) (function is concave up). - \( f''(x) < 0 \) in the intervals \( (0, 3) \) and \( (3, \infty) \) (function is concave down). ### Step 2: Sketching the Graph of \( f(x) \) Based on the properties above, we can sketch the graph of \( f(x) \): - From \( -\infty \) to \( -2 \), \( f(x) \) is increasing and concave up. - At \( x = -2 \), the function has a corner (not differentiable but continuous). - From \( -2 \) to \( 0 \), \( f(x) \) is decreasing and concave down. - At \( x = 0 \), \( f(0) = 0 \). - From \( 0 \) to \( 3 \), \( f(x) \) continues to decrease and approaches \( -\infty \) as \( x \) approaches \( 3 \). - At \( x = 3 \), there is a discontinuity (not continuous). - From \( 3 \) to \( \infty \), \( f(x) \) is increasing and approaches \( 0 \). ### Step 3: Sketching the Graph of \( |x| \) The graph of \( |x| \) is a V-shaped graph that intersects the x-axis at the origin and has a slope of 1 for \( x \geq 0 \) and a slope of -1 for \( x < 0 \). ### Step 4: Finding Intersections To find the maximum number of solutions to \( f(x) = |x| \): 1. **From \( -\infty \) to \( -2 \)**: The function is increasing. It can intersect \( |x| \) once in this interval. 2. **At \( x = -2 \)**: The function has a corner, which can lead to another intersection. 3. **From \( -2 \) to \( 0 \)**: The function is decreasing. It can intersect \( |x| \) once more. 4. **At \( x = 0 \)**: The function intersects \( |x| \) at the origin. 5. **From \( 0 \) to \( 3 \)**: The function is decreasing and approaches \( -\infty \). It can intersect \( |x| \) once more. 6. **From \( 3 \) to \( \infty \)**: The function is increasing and approaches \( 0 \). It can intersect \( |x| \) once more. ### Conclusion Counting all possible intersections, we find: - 1 intersection in \( (-\infty, -2) \) - 1 intersection at \( x = -2 \) - 1 intersection in \( (-2, 0) \) - 1 intersection at \( x = 0 \) - 1 intersection in \( (0, 3) \) - 1 intersection in \( (3, \infty) \) Thus, the maximum possible number of solutions for \( f(x) = |x| \) is **5**.
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