前馈神经网络(ANN)和递归神经网络(RNN)有什么区别

In ANN the equation during Forward Propagation is Y = W.X + b.

What is the equation during Forward Propagation for RNN, as it involves States and Timesteps.

What is the difference between ANN and RNN in terms of Back Propagation.

Also, what is the difference in functionality between Dropout in ANN vs Recurrent_Dropout in RNN.

Are there any other key differences between ANN and RNN.