How do you find the product #(a-3)(a+3)#?

1 Answer
Dec 26, 2016

Answer:

#(a-3)(a+3)=color(green)(a^2-9)#

Explanation:

Either remember the general case
#color(white)("XXX")(p-q)(p+q)=p^2-q^2# (sometimes called "the difference of squares")

...or do the multiplication
#(a-3)(a+3)#
#color(white)("XXX")=(a-3)a + (a-3)3# (using the distributive property)

#color(white)("XXX")=(a^2-3a)+(3a-9)#

#color(white)("XXX")=a^2-9#

(could also be done using FOIL or tabular multiplcation)