Using the FOIL method - Firsts: a×a= a^2 Outers: a×-b= -ab Inners: b×a= ab Lasts: b×-b= -b^2
Combine - a^2-ab+ab-b^2 = a^2-b^2
This particular pair of binomial brackets with a + and a - in them can be expanded with the difference of two squares: (a+b)(a-b) = a^2-b^2 This works for binomial brackets with a + and a - in each of them, and where the two terms in each bracket are the sameFor example: (x+5)(x-5)= x^2-25 So remember, Difference Of Two Squares, Abbreviated as D.O.T.S
F- multiply the first two terms axa= a^2 O- multiply the two terms on the outside a x -b= -ab I- multiply the two inner (middle) terms - b x a= ab L- multiply the last variable in each term= b^2
A shortcut without using FOIL is called the difference of squares and can be rewrote as (a^2-b^2)
