=(x-y)*[(x-y)- 12]+36

=(x-y)^2- 12*(x-y)+36

Error = [(x-y)-4] * [(x-y)-9] ... cross multiplication.

Solution =(x-y-4)(x-y-9)

Note: treat x-y as a whole.

For quadratic polynomial x 2+x+x (where x is a number, but not necessarily the same)

A b

c d

Where ac is the coefficient of x 2, ad+bc is the coefficient of x, and bd is a constant term, for example:

For x 2+5x+6, there are

a= 1 b=2

c= 1 d=3

Note: the decomposition method is not unique, only the one that conforms to the original formula is unique, and it needs to be verified many times by itself.

Then ac= 1 is the coefficient of x 2, ad+bc=5 is the coefficient of x, and bd=6 is a constant term, which shows that this decomposition is correct.

Similarly, the x-y in this question is equivalent to the x above, so

a= 1 b=6

c= 1 d=6

The result is = (x-y-6) 2. Yes, I'm sorry about the calculation error. It is completely flat. You can ask your teacher about cross multiplication. Although you don't say it, it will be very helpful in the future.