$\"\"$

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The revenue function is $\"\"$ .

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(a).

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At what price $\"\"$ ,the revenue is zero.

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Therefore ball will strike the ground at distance $\"\"$

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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

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The revenue is zero where price $\"\"$ is $ $\"\"$ and $ $\"\"$ .

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$\"\"$

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(b).

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The revenue is$ $\"\"$ .

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Therefore substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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Find the vertex of above quadratic function $\"\"$ .

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$\"\"$

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Compare it to $\"\"$ .

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

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Since $\"\"$ , then the parabola open upward.

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$\"\"$

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$\"\"$

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$\"\"$ coordinate of vertex is $\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Vertex $\"\"$

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$\"\"$

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Graph:

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Graph the quadratic equation $\"\"$

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Draw the coordinate plane.

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Plot the intercepts and vertex.

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Connect the plotted points.

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$\"\"$

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observe the graph:

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The price $\"\"$ is in between $ $\"\"$ and $ $\"\"$ .

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Hence $\"\"$ .

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$\"\"$

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(a).The price $\"\"$ is $ $\"\"$ and $ $\"\"$ .

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(b). $\"\"$ .