Equations of Straight Lines Part 1

(i) Slope-intercept form 

Equation of straight line with slope m and y - intercept c is given by: 

                                               y = mx + c

Example

Find the equation of the line with slope is 2 and c=5.

Solution

                                                             y = mx + c

  so                                                        y = 2x + 5

(ii) Point-slope form 

Let m be a slope of line and A(x y 1 1 , ) be a point lies on a line then equation of
line is given by:

 

                                               y - y₁ = m(x - x₁)

Example

Find the equation of the line with gradient 2 passing through (1, 4).

Solution

y - 4 = 2(x - 1)

y - 4 = 2x - 2

y = 2x + 2