Final answer:
To simplify a radical expression, we look for perfect nth powers in the radicand. The expression 3√-5 cannot be simplified, but the expression 4√7 can be simplified to 2√7.
Step-by-step explanation:
To simplify radical expressions, we look for perfect nth powers in the radicand (the number inside the radical symbol). For example, in the expression 3√-5, there are no perfect cubes of -5, so the expression cannot be simplified any further.
However, in 4√7, 7 is a perfect square (3^2), so we can simplify it to 2√7.