Evaluate
30-2\sqrt{5}\approx 25.527864045
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25-10\sqrt{5}+\left(\sqrt{5}\right)^{2}+8\sqrt{5}
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(5-\sqrt{5}\right)^{2}.
25-10\sqrt{5}+5+8\sqrt{5}
The square of \sqrt{5} is 5.
30-10\sqrt{5}+8\sqrt{5}
Add 25 and 5 to get 30.
30-2\sqrt{5}
Combine -10\sqrt{5} and 8\sqrt{5} to get -2\sqrt{5}.
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