Errors found in the `basic_datatypes` notebook

[despadam]

• [ ] Add import math in solution_circle_area() in basic_datatypes and explain that pi is defined there
• [ ] It is not clear that quadratic equation expects two results
• [ ] solution_number_is_lower_than_0_or_greater_than_100 in the test we check for >=
• [ ] in comparison operators, explain the difference of == and isequal with the float number problem and how is it repsresented in bits