Question 33763
{{{ (x-11)(x+11) }}}
Using FOIL .... find the products and then add
F: {{{ x * x = x^2 }}}
O: {{{ x * 11 = 11x }}}
I: {{{ x * -11 = 11x }}}
L: {{{ -11 * 11 = -121 }}}
Add
{{{ x^2 +11x-11x-121 }}}
Combine like terms
{{{ x^2 - 121 }}}
ANY two binomials, when they are the EXACT sam numbers and one of the signs is positive and the other is negative, is considered a special product.  This one being the difference of two squares, and it will always come back into this form:
{{{ x^2 - y^2 = (x-y)(x+y) }}}
Memorize this pattern