Evaluate
4\sqrt{5}\approx 8.94427191
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\sqrt{100-2^{2}\left(\sqrt{5}\right)^{2}}
Expand \left(2\sqrt{5}\right)^{2}.
\sqrt{100-4\left(\sqrt{5}\right)^{2}}
Calculate 2 to the power of 2 and get 4.
\sqrt{100-4\times 5}
The square of \sqrt{5} is 5.
\sqrt{100-20}
Multiply 4 and 5 to get 20.
\sqrt{80}
Subtract 20 from 100 to get 80.
4\sqrt{5}
Factor 80=4^{2}\times 5. Rewrite the square root of the product \sqrt{4^{2}\times 5} as the product of square roots \sqrt{4^{2}}\sqrt{5}. Take the square root of 4^{2}.
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