Evaluate
-5
Factor
-5
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\left(10+5\sqrt{5}\right)\left(2-\sqrt{5}\right)
Use the distributive property to multiply 5 by 2+\sqrt{5}.
20-10\sqrt{5}+10\sqrt{5}-5\left(\sqrt{5}\right)^{2}
Apply the distributive property by multiplying each term of 10+5\sqrt{5} by each term of 2-\sqrt{5}.
20-5\left(\sqrt{5}\right)^{2}
Combine -10\sqrt{5} and 10\sqrt{5} to get 0.
20-5\times 5
The square of \sqrt{5} is 5.
20-25
Multiply -5 and 5 to get -25.
-5
Subtract 25 from 20 to get -5.
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Limits
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