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If (2)/(3)=(x-(1)/(y))+(x^(2)-(1)/(y^(2)...

If `(2)/(3)=(x-(1)/(y))+(x^(2)-(1)/(y^(2)))+ ... "To" oo`
and xy =2 then calculate the values of x and y with the condition that x `lt 1`.

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To solve the problem, we need to find the values of \( x \) and \( y \) given the equation: \[ \frac{2}{3} = \left( x - \frac{1}{y} \right) + \left( x^2 - \frac{1}{y^2} \right) + \left( x^3 - \frac{1}{y^3} \right) + \ldots \] and the condition \( xy = 2 \) with \( x < 1 \). ### Step 1: Identify the series as a geometric series (GP) The series can be separated into two parts: 1. The first part: \( x + x^2 + x^3 + \ldots \) 2. The second part: \( -\left( \frac{1}{y} + \frac{1}{y^2} + \frac{1}{y^3} + \ldots \right) \) Both of these are geometric series. ### Step 2: Sum of the first geometric series The sum of the first geometric series \( x + x^2 + x^3 + \ldots \) can be calculated using the formula for the sum of an infinite geometric series: \[ S_1 = \frac{x}{1 - x} \quad \text{(where the first term is } x \text{ and the common ratio is } x) \] ### Step 3: Sum of the second geometric series The sum of the second geometric series \( \frac{1}{y} + \frac{1}{y^2} + \frac{1}{y^3} + \ldots \) is: \[ S_2 = \frac{\frac{1}{y}}{1 - \frac{1}{y}} = \frac{1/y}{(y-1)/y} = \frac{1}{y - 1} \quad \text{(where the first term is } \frac{1}{y} \text{ and the common ratio is } \frac{1}{y}) \] ### Step 4: Combine the sums Now we can combine these sums into the original equation: \[ \frac{2}{3} = \frac{x}{1 - x} - \frac{1}{y - 1} \] ### Step 5: Substitute \( y \) using \( xy = 2 \) From the condition \( xy = 2 \), we can express \( y \) in terms of \( x \): \[ y = \frac{2}{x} \] Substituting this into the equation gives: \[ \frac{2}{3} = \frac{x}{1 - x} - \frac{1}{\frac{2}{x} - 1} \] ### Step 6: Simplify the equation Substituting \( y \) into the second part of the equation: \[ \frac{2}{3} = \frac{x}{1 - x} - \frac{1}{\frac{2 - x}{x}} = \frac{x}{1 - x} - \frac{x}{2 - x} \] ### Step 7: Find a common denominator The common denominator for the right-hand side is \( (1 - x)(2 - x) \): \[ \frac{2}{3} = \frac{x(2 - x) - x(1 - x)}{(1 - x)(2 - x)} \] ### Step 8: Expand and simplify Expanding the numerator: \[ x(2 - x) - x(1 - x) = 2x - x^2 - x + x^2 = x \] Thus, we have: \[ \frac{2}{3} = \frac{x}{(1 - x)(2 - x)} \] ### Step 9: Cross-multiply Cross-multiplying gives: \[ 2(1 - x)(2 - x) = 3x \] ### Step 10: Expand and rearrange Expanding the left side: \[ 2(2 - 3x + x^2) = 3x \] \[ 4 - 6x + 2x^2 = 3x \] \[ 2x^2 - 9x + 4 = 0 \] ### Step 11: Solve the quadratic equation Using the quadratic formula \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \): \[ x = \frac{9 \pm \sqrt{(-9)^2 - 4 \cdot 2 \cdot 4}}{2 \cdot 2} \] \[ x = \frac{9 \pm \sqrt{81 - 32}}{4} \] \[ x = \frac{9 \pm \sqrt{49}}{4} \] \[ x = \frac{9 \pm 7}{4} \] This gives us two potential solutions for \( x \): 1. \( x = \frac{16}{4} = 4 \) 2. \( x = \frac{2}{4} = \frac{1}{2} \) ### Step 12: Determine the valid solution Since we are given that \( x < 1 \), we take \( x = \frac{1}{2} \). ### Step 13: Calculate \( y \) Using \( xy = 2 \): \[ y = \frac{2}{x} = \frac{2}{\frac{1}{2}} = 4 \] ### Final Answer Thus, the values of \( x \) and \( y \) are: \[ x = \frac{1}{2}, \quad y = 4 \]
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ICSE-SEQUENCE AND SERIES -EXERCISE 14 (f)
  1. Of how many terms is ,(55)/(72) the sum of the series (2)/(9) -(1)/(3...

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  2. The second term of a G.P. is 2 and the sum of infinite terms is 8. Fin...

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  3. Find the value of 0.23434343434..... regarding it as a geometric serie...

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  4. Evaluate : (a) 0.9bar7 (b) 0.2345

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  5. Find a rational number which when expressed as a decimal will have 1.2...

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  6. If a+b+.... + l is a G.P., prove that its sum is (bl-a^(2))/(b-a) .

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  7. The nth term of a geometrical progression is (2^(2n-1))/(3) for all va...

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  8. A geometrical progression of positive terms and an arithmetical progre...

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  9. In a geometric progression, the third term exceeds the second by 6 and...

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  10. In an infinite geometric progression, the sum of first two terms is 6 ...

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  11. Three numbers are in A.P. and their sum is 15. If 1,4 and 19 be added ...

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  12. Calculate the least number of terms of the geometric progression 5 + 1...

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  13. If S is the sum, P the product and R the sum of the reciprocals of n t...

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  14. Find the sum of the first n terms of the series: 0.2 + 0.22 + 0.222+...

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  15. If (2)/(3)=(x-(1)/(y))+(x^(2)-(1)/(y^(2)))+ ... "To" oo and xy =2 th...

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  16. S(1),S(2), S(3),...,S(n) are sums of n infinite geometric progressions...

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  17. Find three numbers a, b, c between 2 and 18 such that: (i) their sum...

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  18. Three numbers, whose sum is 21, are in A.P. If 2, 2, 14 are added to t...

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  19. If X=1+a+a^(2)+a^(3)+"..."+infty " and " y=1+b+b^(2)+b^(3)+"..."+infty...

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  20. If S(1),S(2), S(3),......, S(p) are the sums of infinite geometric ser...

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