Implements multiply

src/recursion.js

@@ -107,11 +107,20 @@ var palindrome = function(string) {
 // modulo(17,5) // 2
 // modulo(22,6) // 4
 var modulo = function(x, y) {
+	if(y=== 0) return NaN;
+	if(x < y) return x;
+	else if(x === y) return 0;
+	else if(x < 0) modulo(x+y, y);
+
+	else return modulo(x-y, y);
 };
 
 // 12. Write a function that multiplies two numbers without using the * operator or
 // Math methods.
 var multiply = function(x, y) {
+	if(x === 0 || y === 0 ) return 0;
+	else if (y < 0) return -x + multiply(x, y + 1);
+  	else return x + multiply(x, y - 1);
 };
 
 // 13. Write a function that divides two numbers without using the / operator or