When the slope is zero then the equation of line will become y = b where b is any value.

When the slope is undefined then the equation of line is x = a where a is any value.

-2y = - x - 6 (add -x on both sides)

y = (-x - 6)/-2 ( divide both side by -2)

y = -x/-2 - 6/-2

y= ½ x +3

Here the slope m = 1/2 and

y intercept b= 3 , y -intercept means x coordinate is 0

Here first mark 3 on the y- axis as the slope is positive ½ so either go up 1 unit up and 2 units to right side from y –intercept or go down 1 unit and 2 units to left. In this way you will get 3 points (including y –intercept) .Join these points and you will get a required graph or a straight line- graph.

If the product of slopes is negative 1 (-1) then the lines are perpendicular to each other.

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