Evaluate
28\sqrt{5}+69\approx 131.60990337
Expand
28 \sqrt{5} + 69 = 131.60990337
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4\left(\sqrt{5}\right)^{2}+28\sqrt{5}+49
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(2\sqrt{5}+7\right)^{2}.
4\times 5+28\sqrt{5}+49
The square of \sqrt{5} is 5.
20+28\sqrt{5}+49
Multiply 4 and 5 to get 20.
69+28\sqrt{5}
Add 20 and 49 to get 69.
4\left(\sqrt{5}\right)^{2}+28\sqrt{5}+49
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(2\sqrt{5}+7\right)^{2}.
4\times 5+28\sqrt{5}+49
The square of \sqrt{5} is 5.
20+28\sqrt{5}+49
Multiply 4 and 5 to get 20.
69+28\sqrt{5}
Add 20 and 49 to get 69.
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