or

(A-B)

(a-b)=(a-b)^2=a^2-2ab+b^2

give rise to

These two formulas are called complete square formulas. The square of the sum (or difference) of two numbers is equal to the sum of the squares of these two numbers, plus (or minus) twice the product of these two numbers.

We usually express it as:

(a+b)^2=a^2+2ab+b^2

note:

Generally, A and B are algebraic expressions representing a whole, not necessarily numbers, such as [(3x-y)-(2x+2y)] [(3x-y)+(2x+2y)] = 5x2+6xy+y2.