HERE'S THE THING ABOUT FUNCTIONS : each input, has exactly ONE output. Not two. ONE. It can be the same output, but you gotta remember this one thing : EACH INPUT VALUE MUST HAVE ONE, AND ONLY ONE VALUE FOR THE OUTPUT, meaning that no two inputs can be the same, basically, though two outputs can be the same. If two inputs were to be the same, it would be as if the input has two outputs, and that just doesn't work out in math, when it comes to functions.
But in other words, the attachment you have added is a function.