Linear equation

linearEquation.js

// f(x) = mx + n
// f(y) = (y - n) / m

var start = {
  x: 1,
  y: 12
}
var end = {
  x: 4,
  y: 0
}

var delta = {
  x : end.x - start.x,
  y : end.y - start.y,
}
var m = delta.y / delta.x
var n = - m * start.x + start.y

var x = 2
var y = m * x + n

console.log(y)