 Let's talk about LSI systems and the first property of linearity. So if we have a signal x1n and it is given to the LSI system and it produces y1n. In other words, we can say that y1n is the system response of x1n. Similarly, y2n is the system response of x2n. Then this property says that a linear combination of these two inputs produces the same linear combination of their individual output signals. Let's take an example where alpha is equal to 2 and beta is minus 1. So if we give a signal twice x1n to the system, we will essentially get twice y1n as output. It is the general case where alpha is 2 and beta is 0. Similarly, if we give minus x2n to the system, we will get minus y2n as the output. Now by the property of linearity, if I give twice x1n minus x2n, I will essentially get twice y1n minus y2n as the output. Now the next property is shift invariance. So let's say yn is the system response of xn. Then this property says that the system response of xn minus capital D is yn minus capital D. That means if we shift the input signal by a certain amount, capital D, the output is also shifted by the same amount. So here it is shifted by 1 and the output is also shifted by 1.