Add files via upload

Author: coder-newbie404

b01/bai18.cpp

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+#include <iostream>
+#include <cmath>
+using namespace std;
+int main()
+{
+    double x1, y1, x2, y2;
+    cin >> x1 >> y1 >> x2 >> y2;
+    cout << sqrt( (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2) );
+    return 0;
+}

b01/bai19.cpp

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+#include <iostream>
+using namespace std;
+int main()
+{
+    int x, y;
+    cin >> x >> y;
+    if (x % 7 == 0 && y % 7 == 0) cout << "true";
+    else cout << "false";
+    return 0;
+}

b01/bai20.cpp

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+#include <iostream>
+#include <cmath>
+using namespace std;
+int main()
+{
+    double x, y, z, p, S;
+    cin >> x >> y >> z;
+    p = (x + y + z) / 2;
+    S = sqrt(p * (p - x) * (p - y) * (p - z));
+    cout << S;
+    return 0;
+}