Evaluate
\sqrt[3]{18}+2\sqrt{21}-3\approx 8.785892784
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\sqrt[3]{18}+2\sqrt{21}-\sqrt{4+\sqrt{25}}
Factor 84=2^{2}\times 21. Rewrite the square root of the product \sqrt{2^{2}\times 21} as the product of square roots \sqrt{2^{2}}\sqrt{21}. Take the square root of 2^{2}.
\sqrt[3]{18}+2\sqrt{21}-\sqrt{4+5}
Calculate the square root of 25 and get 5.
\sqrt[3]{18}+2\sqrt{21}-\sqrt{9}
Add 4 and 5 to get 9.
\sqrt[3]{18}+2\sqrt{21}-3
Calculate the square root of 9 and get 3.
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