Equation of straight lines :
1.General form
The first-degree equation in x and y is known as a general form of a straight line.
Example – ax + by + c = 0 , where a and b are not both zero at a same time.
x = 0 , Y-axis.
y = 0 , X-axis
x = a , parallel to Y-axis.
Y = b, parallel to X-axis.
The distance of a point (x, y ) from x-axis is |y| and from y-axis is |x|.
Slope = -a/b
Intercept on x-axis :
Put y=0.
x = -c/a
Intercept on y-axis:
Put x = 0
y = -c/b
2.Slope form
An equation of a line has slope m = tanθ and cutting off an intercept c on Y-axis.
Then
y = x.tanθ + c
y = mx+c
3. Intercept form
An equation of a straight line L and cutting of an intercepts a and b upon axes of X and Y respectively.
Then
x/a + y/b = 1
if the equation of a straight line L is –
a) parallel to X-axis, X-intercept is not defined.
b) parallel to Y-axis, Y-intercept is not defined.