straight line equations

Question 1

midpoint

Answer 1

( x - x / 2 , y - y / 2)

Question 2

distance between two points

Answer 2

√( (x2-x1)²+(y2-y1)² )

Question 3

gradient

Answer 3

y 2 - y 1 / x2 - x1

m = tan

m x perpendicular gradient = -1

Question 4

collinear

Answer 4

points which lie on the same straight line

Question 5

concurrent

Answer 5

lines all pass through the same point