Question 925919

Substitute {{{0}}} for {{{y}}} in the rule for {{{f(x)}}} and solve for {{{x}}}:
 
{{{f(x)=-4x-8}}}........{{{f(x)=y=0}}}

{{{0=-4x-8}}}

{{{0+4x=-4x+4x-8}}}

{{{4x=-8}}}

{{{x=-8/4}}}

{{{x=-2}}}