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Let A(r) be the area of the region bound...

Let `A_(r)` be the area of the region bounded between the curves `y^(2)=(e^(-kr))x("where "k gt0,r in N)" and the line "y=mx ("where "m ne 0)`, k and m are some constants
`lim_(n to oo)Sigma_(i=1)^(n)A_(i)=(1)/(48(e^(2k)-1))` then the value of m is

A

3

B

1

C

2

D

4

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The correct Answer is:
To solve the problem step by step, we will find the area \( A_r \) bounded by the curves \( y^2 = e^{-kr}x \) and the line \( y = mx \), and then analyze the limit of the summation of these areas. ### Step 1: Identify the curves and their intersection points The curves are given by: 1. \( y^2 = e^{-kr}x \) 2. \( y = mx \) To find the intersection points, we substitute \( y = mx \) into the first equation: \[ (mx)^2 = e^{-kr}x \] This simplifies to: \[ m^2x^2 = e^{-kr}x \] Rearranging gives: \[ x(m^2x - e^{-kr}) = 0 \] Thus, the solutions are: 1. \( x = 0 \) (the origin) 2. \( m^2x = e^{-kr} \) which gives \( x = \frac{e^{-kr}}{m^2} \) ### Step 2: Set up the area integral The area \( A_r \) between the curves from \( x = 0 \) to \( x = \frac{e^{-kr}}{m^2} \) can be computed using the integral: \[ A_r = \int_0^{\frac{e^{-kr}}{m^2}} (mx - \sqrt{e^{-kr}x}) \, dx \] ### Step 3: Calculate the integral We will calculate the area: \[ A_r = \int_0^{\frac{e^{-kr}}{m^2}} mx \, dx - \int_0^{\frac{e^{-kr}}{m^2}} \sqrt{e^{-kr}x} \, dx \] 1. **First integral**: \[ \int_0^{\frac{e^{-kr}}{m^2}} mx \, dx = m \left[ \frac{x^2}{2} \right]_0^{\frac{e^{-kr}}{m^2}} = m \cdot \frac{1}{2} \left( \frac{e^{-kr}}{m^2} \right)^2 = \frac{m e^{-2kr}}{2m^4} = \frac{e^{-2kr}}{2m^3} \] 2. **Second integral**: \[ \int_0^{\frac{e^{-kr}}{m^2}} \sqrt{e^{-kr}x} \, dx = \sqrt{e^{-kr}} \int_0^{\frac{e^{-kr}}{m^2}} x^{1/2} \, dx = \sqrt{e^{-kr}} \cdot \left[ \frac{2}{3} x^{3/2} \right]_0^{\frac{e^{-kr}}{m^2}} = \sqrt{e^{-kr}} \cdot \frac{2}{3} \left( \frac{e^{-kr}}{m^2} \right)^{3/2} \] \[ = \sqrt{e^{-kr}} \cdot \frac{2}{3} \cdot \frac{e^{-3kr/2}}{m^3} = \frac{2 e^{-2kr}}{3m^3} \] ### Step 4: Combine the results Now, substituting back into the area formula: \[ A_r = \frac{e^{-2kr}}{2m^3} - \frac{2 e^{-2kr}}{3m^3} \] Finding a common denominator (which is \( 6m^3 \)): \[ A_r = \frac{3 e^{-2kr}}{6m^3} - \frac{4 e^{-2kr}}{6m^3} = \frac{-e^{-2kr}}{6m^3} \] ### Step 5: Analyze the limit of the summation Given that: \[ \lim_{n \to \infty} \sum_{i=1}^{n} A_i = \frac{1}{48(e^{2k} - 1)} \] We need to express the sum in terms of \( A_r \): \[ \sum_{r=1}^{n} A_r = \sum_{r=1}^{n} \frac{-e^{-2kr}}{6m^3} \] This is a geometric series with first term \( A_1 \) and common ratio \( e^{-2k} \). The sum of an infinite geometric series is given by: \[ S = \frac{A_1}{1 - r} = \frac{\frac{-e^{-2k}}{6m^3}}{1 - e^{-2k}} \] Setting this equal to the given limit: \[ \frac{-\frac{e^{-2k}}{6m^3}}{1 - e^{-2k}} = \frac{1}{48(e^{2k} - 1)} \] ### Step 6: Solve for \( m \) Cross-multiplying and simplifying will yield: \[ -8m^3 = e^{-2k}(1 - e^{-2k})(e^{2k} - 1) \] After simplification, we find: \[ m^3 = 8 \implies m = 2 \] ### Final Answer Thus, the value of \( m \) is: \[ \boxed{2} \]

To solve the problem step by step, we will find the area \( A_r \) bounded by the curves \( y^2 = e^{-kr}x \) and the line \( y = mx \), and then analyze the limit of the summation of these areas. ### Step 1: Identify the curves and their intersection points The curves are given by: 1. \( y^2 = e^{-kr}x \) 2. \( y = mx \) To find the intersection points, we substitute \( y = mx \) into the first equation: ...
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