title: What is the role of the bias in neural networks?
body: <p>I'm aware of the gradient descent and the back-propagation algorithm. What I don't get is: when is using a bias important and how do you use it?</p>
  <p>For example, when mapping the <code>AND</code> function, when I use two inputs and one output, it does not give the correct weights. However, when I use three inputs (one of which is a bias), it gives the correct weights.</p>