When rewriting inequalities it's important to make the the same operation on both sides to ensure that the inequality still holds. If one side is raised to a power, the same operation must be performed on the other side. In the inequality $\sqrt{x}\le 8,$ both sides can be raised to the power of $2.$ However, this operation should only be used when the bases on both sides are positive. Otherwise, we need to divide the inequality into cases and check absolute values.