Math CentralQuandaries & Queries


Question from Natividad:

How do you graph y= -2x-1?


The big step here is to recognize that the graph of $y = -2x - 1$ is a straight line. One you know that, if you graph two points on the line you can join them with a straight line to graph the line. For example if you substitute $x = 0$ into the equation to find the corresponding $y$ value, say $y = ?$, you can plot the point $(0, ?).$ Then try $x = 1$ to find a second point to plot and then join the points using a ruler.

Another technique is to use the fact that $y = -2x - 1$ is in the form $y = mx + b$ with $m = -2$ and $b = -1.$ Hence the slope of the line is -2 and the y-intercept is $(0, -1).$


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