When we make a symmetrie transformation in a quantum system, the state ##|\psi \rangle## change to ## |\psi' \rangle = U|\psi \rangle##, where ##U## is a unitary or antiunitary operator, and the operator ##A## change to ##A'##. If we require that the expections values of operators don't change, we have $$\langle \psi '| A' | \psi ' \rangle= \langle \psi | U^{\dagger}A'U | \psi \rangle =\langle \psi | A | \psi \rangle,$$ what suggest that ##A' = UAU^{\dagger}##. However, in some textbooks, like Sakurai, the change in the operator is ##A' = U^{\dagger}AU##. Why this difference appear? They are equivalent?