$\"\"$

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(a)

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The statement is $\"\"$ .

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

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if $\"\"$ .

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if $\"\"$ .

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Consider $\"\"$ .

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$\"\"$

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

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$\"\"$

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

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$\"\"$ .

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Therefore, $\"\"$ .

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$\"\"$

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(b)

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The expression is $\"\"$ .

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From the above, $\"\"$ .

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$\"\"$

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$\"\"$ .

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Therefore, $\"\"$ .

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$\"\"$

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(a) $\"\"$ .

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(b) $\"\"$ .