Sunday 24 November 2019

algebra precalculus - How to solve $sqrt{9-4sqrt{5}}=$?




Need some hints how to solve this: $\sqrt{9-4\sqrt{5}}=$ ?



Thanks.


Answer



$\sqrt{9-4\sqrt{5}}=\sqrt{5+4-2\cdot 2\cdot \sqrt{5}}=\sqrt{(\sqrt{5}-2)^{2}}=|\sqrt{5}-2|=\sqrt{5}-2$


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