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For (1)/(asqrt(x)+bsqrt(y)) the rational...

For `(1)/(asqrt(x)+bsqrt(y))` the rationalising factor is a `asqrt(x)-bsqrt(y)` .
If `x=(1)/(3-2sqrt(2))` and `y=(1)/(3+2sqrt(2))` , then value of `xy^(2)+x^(2)y` is

A

`4`

B

`12`

C

`6`

D

`9`

Text Solution

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The correct Answer is:
To solve the problem, we need to find the value of \( xy^2 + x^2y \) given that \( x = \frac{1}{3 - 2\sqrt{2}} \) and \( y = \frac{1}{3 + 2\sqrt{2}} \). ### Step-by-Step Solution: 1. **Rationalizing \( x \)**: \[ x = \frac{1}{3 - 2\sqrt{2}} \] To rationalize the denominator, we multiply the numerator and denominator by the conjugate of the denominator: \[ x = \frac{1 \cdot (3 + 2\sqrt{2})}{(3 - 2\sqrt{2})(3 + 2\sqrt{2})} \] The denominator simplifies as follows: \[ (3 - 2\sqrt{2})(3 + 2\sqrt{2}) = 3^2 - (2\sqrt{2})^2 = 9 - 8 = 1 \] Therefore: \[ x = 3 + 2\sqrt{2} \] 2. **Rationalizing \( y \)**: \[ y = \frac{1}{3 + 2\sqrt{2}} \] Similarly, we rationalize \( y \) by multiplying by the conjugate: \[ y = \frac{1 \cdot (3 - 2\sqrt{2})}{(3 + 2\sqrt{2})(3 - 2\sqrt{2})} \] The denominator simplifies to: \[ (3 + 2\sqrt{2})(3 - 2\sqrt{2}) = 3^2 - (2\sqrt{2})^2 = 9 - 8 = 1 \] Therefore: \[ y = 3 - 2\sqrt{2} \] 3. **Calculating \( xy^2 + x^2y \)**: We can factor the expression: \[ xy^2 + x^2y = xy(y + x) \] First, we find \( x + y \): \[ x + y = (3 + 2\sqrt{2}) + (3 - 2\sqrt{2}) = 6 \] 4. **Calculating \( xy \)**: Now we find \( xy \): \[ xy = (3 + 2\sqrt{2})(3 - 2\sqrt{2}) = 3^2 - (2\sqrt{2})^2 = 9 - 8 = 1 \] 5. **Final Calculation**: Now substituting back into the expression: \[ xy^2 + x^2y = xy(y + x) = 1 \cdot 6 = 6 \] Thus, the value of \( xy^2 + x^2y \) is \( \boxed{6} \).
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