$\"\"$ $\"\"$

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Slope formulae $\"\"$ .

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ (Product of two sames signs is positive)

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$\"\"$ (Add: $\"\"$ )

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$\"\"$ (Add: $\"\"$ )

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$\"\"$ (Cancel common terms) $\"\"$

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Slope is $\"\"$ .