How do you graph  3x+y=-6?

May 25, 2016

Change the equation into standard form, $y = m x + c$
Then either plot points or use the y-intercept and the gradient.

Explanation:

The y-intercept is -6. This is the first obvious point.
To find the x-intercept, make y = 0:
$0 = - 3 x - 6 \Rightarrow 0 = 3 x + 6$
Now solve for x: $3 x = - 6 , \Rightarrow x = - 2$

These two points are enough,but it is better to have a few more to check.

The gradient is -3. This is better written as $\frac{- 3}{1}$

From -6 on the y-axis, count UP 3 units and LEFT 1 unit and mark the point. (-1,3). Repeat this a few times which will give the points
(-2, 0), (-3,3) (-4,6) (-5,9)

These can be joined with a straight line to give the graph.