Question 1120460
Middle of the dish sits on origin of cartesian system.  Cross section may be {{{y=ax^2}}}, and three points are  (0,0), (8,12), and (-8,12).


{{{a=y/x^2}}}

{{{a=12/8^2=(4*3)/(4*2*8)}}}

{{{a=3/16}}}


{{{y=(3/16)x^2}}}


{{{highlight((16/3)y=x^2)}}}

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FOCUS AND LOCATION OF BULB

p, distance from vertex to bulb


{{{4p=16/3}}}

{{{p=(16/3)(1/4)}}}

{{{p=4/3}}}

Bulb is  {{{1&1/3}}} inches above the vertex or middle point of the satellite dish, in the concave region.