5(sqrt{20}) - 2(sqrt{125})
You need to simplify the square roots individually.
For each square root, look for two numbers that, when multiplied, will yield the number inside the radicand. However, one of the factors has to be a perfect square.
sqrt{20} = sqrt{4} times sqrt{5}
The square root of 4 is a perfect square because 2 times 2 = 4.
Then, the square root of 4 = 2.
The square root of 5 is NOT a perfect square and it is also in lowest term.
So, leave it alone.
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sqrt{125} = sqrt{25} times sqrt{5}
The square root of 25 is 5 because 5 times 5 = 25.
Then, the square root of 25 is 5.
Again, the square root of 5 is NOT a perfect square and it is also in lowest term. Leave it alone.
We now have this:
5(2)(sqrt{5}) - 2(5)(sqrt{5})
10(sqrt{5}) - 10(sqrt(5}) = 0
The answer is 0.