$\"\"$

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The standard form of quadratic equation in x - variables is $\"\"$ , where $\"\"$ .

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The equation is $\"\"$ .

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Add $\"\"$ to each side.

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$\"\"$

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$\"\"$

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Subtract 80 from each side.

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$\"\"$

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

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Graph the related function $\"\"$ .

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$\"graph$

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Observe the graph, the graph intersect the x - axis at two points $\"\"$ .

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So the equation two solutions and the solutions are $\"\"$ . $\"\"$

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To check the first solution, the value of $\"\"$ substitute in the original equation, $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ (Solution checks) $\"\"$

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To check the first solution, the value of $\"\"$ substitute in the original equation, $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ (Solution checks) $\"\"$

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The solution are $\"\"$ .