We'll start by rewriting this as the addition of the opposite. (Subtractions, especially with negative numbers, are too often a rich source of errors.):
Like radical terms have the same type of root with the same radicands. (The expression inside a radical is called the radicand.) Your terms both have square roots and both arguments of the square roots are 20's. So these are like terms and we can add them. And how do we add these terms? Answer: Exactly like 2.118x + 0.138x = 2.256x,
The only thing left to do is simplify the square root. The radicand of the square root, 20, has a prefect square factor so it will simplify:
Now we use a property of radicals, to split the square root of the product into the product of the square roots of the factors:
The square root of the perfect square simplifies:
which simplifies to:
This is the fully simplified answer.
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