$\"\"$

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(a)

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Observe the diagram.

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The radius of the circle is $\"\"$ .

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The equation of the circle: $\"\"$ .

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Substitute $\"\"$ in above equation.

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$\"\"$

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The equation of the circle at the current time is $\"\"$ .

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The fire reaches the city, the radius will be $\"\"$ .

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

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$\"\"$

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The equation of the circle at the time the fire reaches the city is $\"\"$ .

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$\"\"$

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(b)

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Graph :

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Graph the functions $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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(c)

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The radius of the fire is growing $\"\"$ per day.

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The city is located $\"\"$ southeast of the fire.

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Thus, the fire reached to the city in $\"\"$ days.

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$\"\"$

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(a)

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The equation of the circle at the current time is $\"\"$ .

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The equation of the circle at the time the fire reaches the city is $\"\"$ .

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(b)

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Graph the functions $\"\"$ and $\"\"$ .

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$\"\"$

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(c)

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The fire reached to the city in $\"\"$ days.