#include<bits/stdc++.h>
using namespace std;
void add(double xa, double xb, double ya, double yb){
double a = xa + ya;
double b = xb + yb;
printf("%.1f %.1f\n", a, b);
}
void mutiply(double xa, double xb, double ya, double yb){
double a = xa*ya - xb*yb;
do...