Question 309038
Let {{{z=sqrt(5)}}} to get the expression {{{(z+2)(z-6)}}}



{{{(z+2)(z-6)}}} Start with the given expression.



{{{z^2-6z+2z-12}}} FOIL



{{{z^2-4z-12}}} Combine like terms.



{{{(sqrt(5))^2-4*sqrt(5)-12}}} Plug in {{{z=sqrt(5)}}}



{{{5-4*sqrt(5)-12}}} Square {{{sqrt(5)}}} to get {{{5}}}



{{{-7-4*sqrt(5)}}} Combine like terms.



So {{{(sqrt(5)+2)(sqrt(5)-6)=-7-4*sqrt(5)}}}