solve them

1. Why do we include the header file iostream in C++ programs? What header file needs to be included in a C++ program when the program uses mathematics formulas such as a-pow (4.0, 2.0)? 2. Write a statement in C++ for the program to display the numeric value of a variable called numericVariable with 3 significant digits? 3. In this particular case in question 3, what header file needs to be included in the program? 4. What will be the value stored in variable X after the execution of the following statements 5. int X, Y, Z; X-Y=5; Xt=Y-2