$\"\"$

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The function is $\"\"$ .

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The tangent line of the function is horizontal, means that, the slope of the tangent line is zero.

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Set slope = $\"image\"$ .

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$\"\"$

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Apply derivative with respect to x.

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$\"image\"$

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Apply formula : $\"image\"$ .

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Apply power rule of derivatives : $\"image\"$ .

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$\"image\"$

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$\"\"$

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Solve $\"image\"$ .

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$\"\"$

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If $\"image\"$ , then the general solution is $\"image\"$ , where $\"image\"$ is an integer.

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$\"\"$ .

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If $\"image\"$ , then $\"\"$ ,

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If $\"image\"$ , then $\"\"$ ,

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If $\"image\"$ , then $\"\"$ , and ..............

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At $\"\"$ , $\"\"$

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At $\"\"$ , $\"\"$

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At $\"\"$ , $\"\"$ , and .........

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The points on the graph of the function are $\"\"$ , where $\"image\"$ is an integer.

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$\"\"$

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Solve $\"image\"$ .

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$\"image\"$

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If $\"image\"$ , then the general solution is $\"image\"$ , where $\"image\"$ is an integer.

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$\"image\"$ .

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If $\"image\"$ , then $\"image\"$ ,

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If $\"image\"$ , then $\"image\"$ ,

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If $\"image\"$ , then $\"image\"$ , and ..............

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At $\"image\"$ , $\"image\"$ .

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At $\"image\"$ , $\"image\"$ .

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At $\"image\"$ , $\"image\"$ , and .........

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The points on the graph of the function are $\"\"$ , where $\"image\"$ is an integer.

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$\"\"$

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The points on the graph which makes gives horizontal tangent are $\"\"$ and $\"\"$ , where $\"image\"$ is an integer.