Question 250613
{{{x=-b/2a}}} will give you the vertex and the axis of symmetry.
{{{b=7}}}
{{{a=-1}}}
{{{x=-7/2=3.5}}}
You can then plot points equidistant from the vertex (they have the same y value).
x=3 and x=4 would give the same y, y=-9+21-2=10
x=2 and x=5 would give the same y, y=-4+14-2=8
x=1 and x=6 would give the same y, y=-1+7-2=4
x=0 and x=7 would give the same y, y=0+0-2=-2
{{{drawing( 300, 300, -2,12, -2, 12,grid( 1 ),
green(line(3.5,-20,3.5,20)),
circle( 3, 10, .2 ),
circle( 4, 10, .2 ),
circle( 2, 8, .2 ),
circle( 5, 8, .2 ),
circle( 1, 4, .2 ),
circle( 6, 4, .2 ),
circle( 0, -2, .2 ),
circle( 7, -2, .2 ),
circle( 3.5, 10.25, .2 ),

graph( 300, 300, -2,12, -2, 12, -x^2+7x-2) )}}}