To see exactly what is going on, replace those "(2- x)" terms by the single letter, a. That is and since there is an " " in each term we can factor it out: .
Now put (2-x) back in place of each "a":
Hello, please look at the picture below.
I don't know where that 3 went... Please tell me?
Also the next problem that starts from 4(3-....
the three goes missing again. Could you tell me how it works??
Thank you!