# 6.1 Revise of Important Concept (Straight Line)

(A) Equation of a straight Line

An equation of straight line is given by y = mx + c.
The variables x and y are linearly related
The term c is known as y-intercept. It represents the y value where the line cuts the y-axis
The term m is the gradient of the straight line and its value is constant

(B) Gradient of a Straight Line
If the points $A\left({x}_{1},{y}_{1}\right)$  and $B\left({x}_{2},{y}_{2}\right)$   lie on the straight line $y=mx+c$ , then gradient of ,the straight line
$m = y 2 − y 1 x 2 − x 1 o r y 1 − y 2 x 1 − x 2$

(C) Mid Point

Mid Point AB is given by $M = ( x 1 + x 2 2 , y 1 + y 2 2 )$

(D) Distance Between Two Points
Distance between point $A\left({x}_{1},{y}_{1}\right)$ and point is $B\left({x}_{2},{y}_{2}\right)$ given by $( x 1 − x 2 ) 2 + ( y 1 − y 2 ) 2$