1。 The teacher should have said (a-b) 2 = a 2-2ab+b 2, so (A2-2AB+B2+5) (-A2+2AB-B2+5) = [5+(A-B) 2] [

2。 If x=0, then the constant terms a0=- 1, x= 1 are replaced by a5+a4+a3+a2+a 1=2, and x=- 1 is replaced by -A5+A4-A3+A2-A65444.

First, each item in this multiplication result is multiplied by one of the multiplied brackets. Let's talk about the simplest (A-B) (A-B) = A 2-AB-AB+B 2. Here, the result is initially four items, and all items are multiplied by one item in each bracket, for example, a× a = a 2. Another example is (a-b) (a-b) (a-b) = a 3+3ab2-a2b-b3, which starts with nine terms. For example, a 3 times three A's, two brackets choose A, and the other one chooses (-b), and the term is-A..

Extending to (2x-1) (2x-1) (2x-1) (2x-1), to form an item like x 5, you need to multiply 2x in each bracket.