Question

Which point is not on the graph represented by y=x^2+2x-4

Answer 1

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

$(-4,4) \\ x=-4 \\ y=4 \\ \Downarrow \\ 4 \stackrel{?}{=} (-4)^2+2 \times (-4)-4 \\ 4 \stackrel{?}{=} 16-8-4 \\ 4 \stackrel{?}{=} 4 \\ 4 = 4 \\ \hbox{the point is on the graph}$

Both points are on the graph.