$\"\"$ \ \

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(a) \ \

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The equation is $\"\"$ .

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Where $\"\"$ are the sizes of the two organs in an organism of age $\"\"$ .

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Find the expression for $\"\"$ as a function of $\"\"$ is $\"\"$ .

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$\"\"$ .

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Integrate on both sides.

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Take exponential function on both sides.

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Therefore,the expression for $\"\"$ as a function of $\"\"$ is $\"\"$ . $\"\"$

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(b)

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The expression for $\"\"$ as a function of $\"\"$ is $\"\"$ .

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

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$\"\"$

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Substitute proprtionality constnat $\"\"$ . \ \

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$\"\"$

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Therefore, the expression for $\"\"$ as a function of $\"\"$ is $\"\"$ .

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$\"\"$

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(a) The expression for $\"\"$ as a function of $\"\"$ is $\"\"$ .

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(b) The expression for $\"\"$ as a function of $\"\"$ is $\"\"$ .