math (algebra honors) #2

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If the radius of a circle is increased by 6 cm, the new area is 121 (pi) cm^2. Find the radius of the original border using factoring.

  • math (algebra honors) #2 -

    the answer is 5 by common sense, i would reevaluate your schools "honours" program

    the area of a circle is pi(r^2)

    therefore pi(x+6)^2=121pi
    now just solve
    (x+6)^2=121
    x+6=11
    x=5

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