$\"\"$

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From the mapping diagram, the functions are $\"\"$ .

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Write the above two functions as co-ordinate points.

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$\"\"$

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$\"\"$ .

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Substitute the values of $\"\"$ in the slope formula $\"\"$ .

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$\"\"$ . $\"\"$

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To find the y - intercept, substitute the values of $\"\"$ in the slope - intercept from of equation $\"\"$ and solve for b.

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$\"\"$

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$\"\"$

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Subtract 3 from each side.

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$\"\"$

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$\"\"$

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$\"\"$ .

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Substitute the values of $\"\"$ in the slope - intercept form of equation $\"\"$ .

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The line equation is $\"\"$ . $\"\"$

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The linear function is $\"\"$ .