Solution - Properties of a straight line

Rearrange:

Rearrange the equation by subtracting what is to the right of the equal sign from both sides of the equation :

                     -4*x-9*y-(4)=0 

Step  1  :

Pulling out like terms :

 1.1     Pull out like factors :

   -4x - 9y - 4  =   -1 • (4x + 9y + 4) 

Equation at the end of step  1  :

Step  2  :

Equation of a Straight Line

 2.1     Solve   -4x-9y-4  = 0

Tiger recognizes that we have here an equation of a straight line. Such an equation is usually written y=mx+b ("y=mx+c" in the UK).

"y=mx+b" is the formula of a straight line drawn on Cartesian coordinate system in which "y" is the vertical axis and "x" the horizontal axis.

In this formula :

y tells us how far up the line goes
x tells us how far along
m is the Slope or Gradient i.e. how steep the line is
b is the Y-intercept i.e. where the line crosses the Y axis

The X and Y intercepts and the Slope are called the line properties. We shall now graph the line  -4x-9y-4  = 0 and calculate its properties

Graph of a Straight Line :

Calculate the Y-Intercept :

Notice that when x = 0 the value of y is 4/-9 so this line "cuts" the y axis at y=-0.44444

  y-intercept = 4/-9  = -0.44444 

Calculate the X-Intercept :

When y = 0 the value of x is 1/-1 Our line therefore "cuts" the x axis at x=-1.00000

  x-intercept = 4/-4 = 1/-1  = -1.00000 

Calculate the Slope :

Slope is defined as the change in y divided by the change in x. We note that for x=0, the value of y is -0.444 and for x=2.000, the value of y is -1.333. So, for a change of 2.000 in x (The change in x is sometimes referred to as "RUN") we get a change of -1.333 - (-0.444) = -0.889 in y. (The change in y is sometimes referred to as "RISE" and the Slope is m = RISE / RUN)

    Slope     = -0.889/2.000 = -0.444 

Geometric figure: Straight Line

1.   Slope = -0.889/2.000 = -0.444
2.   x-intercept = 4/-4 = 1/-1 = -1.00000
3.   y-intercept = 4/-9 = -0.44444