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The coordinates are $\"\"$ and $\"\"$ .

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Formula for the slope is $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Slope of the line joining points is $\"\"$ .

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But he states that slope is $\"\"$ .

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He forgot the negative sign of the slope.

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Slope of the line joining points is $\"\"$ .

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He forgot the negative sign of the slope.