Hello All, There is a gap in my knowledge with difference equations. I can not relate a difference equation that has been determined by inspection from a signal flow diagram and difference equations that are solved using the complementary function and particular integral method. An example of a difference equation determined from a diagram may look something like this: This difference equation incudes a shifted and scaled versions of the input and also feedback of the output which is delayed and scaled. However whenever I look at examples of difference equations that are to be solved never have the input in them, they just include the output on the right and input on the left This makes sense I just don't know how we get to here. I can compare it to continuous time functions for example a differential equation that describes a series RC circuit. This is then solved for vC, in the same way the difference equation has y terms on the right and input on the left, the solution is determine for y[n]. But I don't understand what happens to the x[n] terms. Would appreciate some help on understanding this.