# Straight Line

**Any equation with the degree of equation being one is known as an equation of straight line. General equation of straight line is given by**

*aX*+

*bY*+

*c*= 0, where

*X*and

*Y*are variables and

*a*,

*b*,

*c*are constants.

Any point lying on this line will satisfy the equation of the line.

If

*AB*is a straight line on the*XY*plane, then the angle q which the line makes with the X-axis in the anti-clockwise direction is called the inclination of the line and tangent of this angle q (tan q) is called the slope of the line*AB*. It is denoted by â€˜*m*â€™. The lengths*OP*and*OQ*are respectively known as the intercepts on X-axis and Y-axis, made by the line.# Slope-intercept form: Different Forms of a Straight Line

*y*=

*mx*+

*c*

*m*â€™ is the slope of the line and â€˜

*c*â€™ the intercept made by the line on Y-axis, the equation is

*y*=

*mx*+

*c*

# Point-slope form: Different Forms of a Straight Line

If 'm' is the slope of the line and it passes through the point, the equation is (x_{1,}y

_{1}), then the equation of the line is given by:

*y*-

*y*=

_{1}*m*(

*x*-

*x*)

_{1}# Two-point form: Different Forms of a Straight Line

**If the line passes through two points (**

*X*,

_{1}*y*) and (

_{1}*X*,

_{2}*Y*) the equation is

_{2}â€‹

â€‹

Using point-slope form and two-point form, we can find out the formula for slope also. Comparing the two equations, we get

*m***=**# Slope-intercept form: Different Forms of a Straight Line

**If the line makes an intercept of**

*a*units on X-axis and

*b*units on Y-axis, then the equation is:

â€‹

â€‹

**Finding Slope of a line:**

- If equation of the line is
*ax*+*by*=*c*, then slope of line =*x*+ 3*y*= 5 is - if two points (
*x*_{1},*y*_{1}) and (*x*_{2},*y*_{2}) are given, then slope of line =