$\"\"$

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(a).

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Harmonic mean of $\"\"$ and $\"\"$ is $\"\"$ .

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The average of $\"\"$ and $\"\"$ is $\"\"$ .

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Equation for which the solution is the harmonic mean of $\"\"$ and $\"\"$ .

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$\"\"$ .

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Now subustiute the values $\"\"$ and $\"\"$ in the above equation.

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$\"\"$ .

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(b).

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Solve the value of $\"\"$ from the above equation.

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$\"\"$

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By using the L.C.M the denominator obtained is $\"\"$ .

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$\"\"$

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The harmonic mean of $\"\"$ and $\"\"$ is $\"\"$ .

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$\"\"$

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(a). Equation is $\"\"$ .

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(b). The harmonic mean of $\"\"$ and $\"\"$ is $\"\"$ .