See the graph below:
Work Step by Step
The graph of the equation, $y=-2x$ is the straight line that passes through the origin and passes through the points $\left( -1,2 \right),\left( 0,0 \right),\left( 1,-2 \right)$. And after comparing the equation $y=-2x$ with $y=mx+c$, we see that the slope is $m=-2$. The arrows on the left and the right of the curve indicate that that it extends indefinitely in both directions.