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2\pi r^{2}
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2\pi r^{2}
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\pi \times 3^{2}r^{2}-7\pi r^{2}
Expand \left(3r\right)^{2}.
\pi \times 9r^{2}-7\pi r^{2}
Calculate 3 to the power of 2 and get 9.
2\pi r^{2}
Combine \pi \times 9r^{2} and -7\pi r^{2} to get 2\pi r^{2}.
\pi \times 3^{2}r^{2}-7\pi r^{2}
Expand \left(3r\right)^{2}.
\pi \times 9r^{2}-7\pi r^{2}
Calculate 3 to the power of 2 and get 9.
2\pi r^{2}
Combine \pi \times 9r^{2} and -7\pi r^{2} to get 2\pi r^{2}.
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