The Equation of a Straight Line & Parallel and Perpendicular Lines

Question 1

What are the three equations that can be used to describe a straight line?

Answer 1

• y-b = m(x-a) for point (a,b) on the line
• y = mx+c
• ax+by+c = 0 where a, b and c are integers

Question 2

What is the equation for the midpoint of a line segment?

Answer 2

Midpoint of the line (ab) = ((xa+xb)/2 , (ya+yb)/2)

Question 3

How do you find the length of a line segment?

Answer 3

Pythagoras’ Theorem: length of line (ab)^2 = (xb-xa)^2 + (yb - ya)^2