\((-6,20) \\
x=-6 \\ y=20 \\ \Downarrow \\
20 \stackrel{?}{=} (-6)^2+2 \times (-6)-4 \\
20 \stackrel{?}{=} 36-12-4 \\
20 \stackrel{?}{=} 20 \\
20 = 20 \\
\hbox{the point is on the graph}\)
\((-4,4) \\
x=-4 \\ y=4 \\ \Downarrow \\
4 \stackrel{?}{=} (-4)^2+2 \times (-4)-4 \\
4 \stackrel{?}{=} 16-8-4 \\
4 \stackrel{?}{=} 4 \\
4 = 4 \\
\hbox{the point is on the graph}\)
Both points are on the graph.
