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The inner circle is x2 + y2 = 4. The radius of the inner circle is the square root of 4, which is 2. To find the radius of the outer circle, multiply 2 times 4. The radius of the outer circle is 8. Square 8 (82 or 8 x 8) to find the number to put into the equation of the outer circle. This is 64. The equation for the outer circle is x2 + y2 = 64.

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Q: The equation of the inner circle is x2 plus y2 equals 4 the radius of the outer circle is four times the radius of the inner circle write the equation of the outer circle?

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