Question 407311
Definition

The {{{x-intercept}}} of a line is the point at which the line
crosses the {{{x}}} axis. ( where the {{{y}}} value equals {{{0}}} )

{{{x-intercept}}} = ( {{{x}}},{{{ 0}}} )

The {{{y-intercept}}} of a line is the point at which the line
crosses the {{{y}}} axis. (  where the {{{x}}} value equals {{{0}}} )

{{{y-intercept}}} = ( {{{0}}}, {{{y}}} )



{{{y=-4x^2-4x+8}}}.........plug the {{{y}}} value equals {{{0}}} 


{{{0=-4x^2-4x+8}}}........use quadratic formula



{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} .....you have {{{a=-4}}}, 

{{{b=-4}}},  {{{c=8}}}



{{{x = (-(-4) +- sqrt((-4)^2-4*(-4)*8 ))/(2*(-4)) }}}


{{{x = (4 +- sqrt( (16+128 ))/(-8)) }}}


{{{x = (4 +- sqrt( 144 )/(-8)) }}}


{{{x = (4 +-  12 )/-8 }}}



{{{x1 = (4 +12 )/-8 }}}
{{{x1 = 16/-8 }}}
{{{x1 = -2 }}



{{{x2 = (4 -12 )/-8 }}}
{{{x2 = -8/-8 }}}
{{{x2 = 1 }}}

let's graph it:


{{{ graph( 500, 500, -10, 10, -10, 10,-4x^2-4x+8) }}}