Write a quadratic function rule for the following table
x -10 -5 0 5 10
y 80 5 -20 5 80
SKETCH A GRAPH !! Always
note
symmetric about x = 0
note
hits bottom at (0,-20) (so that is the vertex)
so
(y +20) = a x^2
at (10,80)
100 = a(100)
a = 1
so I claim
x^2 = y + 20