Evaluate
8-2\sqrt{7}\approx 2.708497378
Expand
8-2\sqrt{7}
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\left(\sqrt{7}\right)^{2}-2\sqrt{7}+1
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(\sqrt{7}-1\right)^{2}.
7-2\sqrt{7}+1
The square of \sqrt{7} is 7.
8-2\sqrt{7}
Add 7 and 1 to get 8.
\left(\sqrt{7}\right)^{2}-2\sqrt{7}+1
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(\sqrt{7}-1\right)^{2}.
7-2\sqrt{7}+1
The square of \sqrt{7} is 7.
8-2\sqrt{7}
Add 7 and 1 to get 8.
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