Question 489262
{{{f(x)=-x^2+3x+28}}}

to find the {{{x-intercept}}}: set {{{f(x)=0}}} 

{{{0=-x^2+3x+28}}}...use quadratic formula


{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} ...{{{a=-1}}}, {{{b=3}}}, and {{{c=28}}}


{{{x = (-3 +- sqrt( 3^2-4*(-1)*28 ))/(2*(-1)) }}} 


{{{x = (-3 +- sqrt( 9+4*28 ))/(-2) }}} 


{{{x = (-3 +- sqrt( 112))/(-2) }}} 


{{{x = (-3 +- 10.58)/(-2) }}} 

solutions:

{{{x = (-3 +10.58)/(-2) }}} 

{{{x = (7.58)/(-2) }}}

{{{x = -3.79 }}}...round it to whole number

{{{x = -4 }}}

or

{{{x = (-3 -10.58)/(-2) }}} 

{{{x = (-13.58)/(-2) }}}

{{{x = 6.79 }}}..round it to whole number

 {{{x = 7 }}}

to find the {{{y-intercept}}}: set {{{x=0}}} 

{{{f(x)=-0^2+3*0+28}}}

{{{f(x)=28}}}

let see it on a graph

{{{ graph( 500, 500, -15, 15, -10, 35, -x^2+3x+28) }}}