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 :

                     y-(21*x+21)=0 

Step  1  :

Equation of a Straight Line

 1.1     Solve   y-21x-21  = 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  y-21x-21  = 0 and calculate its properties

Graph of a Straight Line :

Calculate the Y-Intercept :

Notice that when x = 0 the value of y is 21/1 so this line "cuts" the y axis at y=21.00000

  y-intercept = 21/1  = 21.00000 

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 = 21/-21 = 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 21.000 and for x=2.000, the value of y is 63.000. So, for a change of 2.000 in x (The change in x is sometimes referred to as "RUN") we get a change of 63.000 - 21.000 = 42.000 in y. (The change in y is sometimes referred to as "RISE" and the Slope is m = RISE / RUN)

    Slope     = 42.000/2.000 = 21.000 

Geometric figure: Straight Line

1.   Slope = 42.000/2.000 = 21.000
2.   x-intercept = 21/-21 = 1/-1 = -1.00000
3.   y-intercept = 21/1 = 21.00000