Random math crap that helps you with tedious school math

findMidpointFromPointsAndRatio.js

// Find a point between two points that fits a certain ratio of distance to both of them
function findMidpointFromPointsAndRatio(a, b, c, d, f = 1, g = 1) {
  /**
    Example: The coordinates of the endpoints of Line ST are S(10, 2) and T(17, 16). 
    Point U is on ST and divides it such that SU:TU is 2:5.
    How the function would be called: findMidpointFromPointsAndRatio(10, 2, 17, 16, 2, 5);
    What it should return: Array [12, 6]
  **/
  const h = f+g;
  return [a + f*(c-a)/h, b + f*(d-b)/h];
}

quadratic_from_intercepts.js

function quadraticFromPoints(r1, r2, p) {
  // Supply root 1, root 2, and an extra point outside of those 2
  var aValue = p[1]/(p[0]**2-r1*p[0]-r2*p[0]+r1*r2);
  var bValue = -aValue*(r1+r2);
  var cValue = aValue*r1*r2;
  
  return `${aValue === 1 ? "" : aValue}x^2${(bValue >= 0 ? "+" : "") + bValue}x${(cValue >= 0 ? "+" : "") + cValue}`;
}

console.log(quadraticFromPoints(-1, -1, [4, 125]));
// This should return 5x^2+10x+5. Edit the values to your liking, then test if they're correct

quadratic_from_vertex.js

function quadraticFromVertex(vertex, point) {
  // Supply [x, y] for both the vertex and point
  var h = vertex[0];
  var k = vertex[1];
  var x = point[0];
  var y = point[1];
  
  var aValue = (y-k)/(x**2-2*x*h+h**2);
  var bValue = aValue * -2 * h;
  var cValue = aValue * h**2 + k;
  
  return `${aValue === 1 ? "" : aValue}x^2${(bValue >= 0 ? "+" : "") + bValue}x${(cValue >= 0 ? "+" : "") + cValue}`;
}

console.log(quadraticFromVertex([-3, 4], [-2, 2]));
// Should return -2x^2-12x-14. Tweak the values to your liking