A grey scale image is an array of intensity values (encoded in some manner often an integers in the range 0-255) where and are the horizontal and vertical pixel indices.

So an image is an array . Here we have a pair of images and and is the absolute value of the difference between the images.

For equations 2 you do not solve for amd you write some code to find the required values.

For you will have to go back to the source and look for its definition, it is some sort of small constant.

CB