$\"\"$

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The equation is $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ and $\"\"$

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$\"\"$ and $\"\"$ .

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$\"\"$ and $\"\"$ .

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The general solution of $\"\"$ is $\"\"$ .

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$\"\"$ , $\"\"$ , $\"\"$ .

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$\"\"$

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$\"\"$ , $\"\"$ , $\"\"$ .