Isolate the radical, square both sides, then check every solution in the original equation. Squaring can add extras. Rational expressions are a different algebra family, in rational expressions.
Check after you square
√(x + 3) = x − 1 can produce a value that makes the original false. Plug back in, in plugging the answer back in. Exponent rules for the square itself are in exponent rules.
The short list is in ACT Math formulas.
The bottom line
Isolate, square, substitute. Discard anything that fails the original.
Start practicing
Start with a free diagnostic, then drill your weak spots with 15-question quizzes and track how you're doing across Reading, English, and Math. Compare plans whenever you're ready to go further.
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