The equation of a straight line is expressed as:

y = mx + b

Where m is the slope of the line, which indicates how steep the line is, and b is the y intercept (which is the point the line crosses the y-axis).

For the straight line in above diagram, b=2, m = 1.2/1=1.2, so the equation of the straight line is:

With that equation you can now choose any value for x and find the matching value for y. For example, when x is 3, y = 1.2 * 3 + 2 = 5.6, and when x is 0, y = 1.2 * 0 + 2 = 2.

Note also that the slope m can be positive, zero, or negative.

When the slopes of 2 lines are equal, these 2 lines are parallel. When a line with a slope of m is perpendicular to another line with a slope of n, then