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You can only add equivalent radicals. For example:

You can add radical expressions that have the same radical parts by adding coefficients. For example:

You can also subtract radicals in the same way:

In some cases, you can add or subtract radical expressions with non-equivalent radical parts by simplifying them using the factoring method I describe in the previous section. For example, here’s an SAT question that depends upon your understanding this idea:

Which of the following is equivalent to ?

(A)

(B)

(C)

(D)

Begin by factoring and to simplify them:

Now, rewrite and solve it:

So Answer C is correct.