**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.