No, the Casio FX-991ES calculator does not have the capability to save functions. It is a scientific calculator designed for performing various mathematical calculations, but it does not have a memory function to save and store functions for later use. If you need to save functions, you may need to use a graphing calculator or a computer software program that allows for function storage and retrieval. **

Yes, the FX-991ES from Casio is a CAS (Computer Algebra System) calculator. It is capable of performing symbolic algebraic calculations, such as solving equations, manipulating expressions, and performing calculus operations. This makes it a powerful tool for students and professionals in fields such as mathematics, engineering, and science. **

The Casio fx 991ES Plus may not be working due to a variety of reasons. It could be a result of a drained battery, a malfunctioning display, or a software issue. It is also possible that the calculator is not turning on due to physical damage or a loose connection. In any case, it is recommended to check the battery, inspect the display, and try resetting the calculator to troubleshoot the issue. If the problem persists, it may be necessary to seek professional assistance or consider replacing the calculator. **

The Casio fx 991ES Plus calculator is a scientific calculator model. It is designed to handle complex mathematical calculations, including trigonometric, logarithmic, and statistical functions. The calculator is popular among students, engineers, and professionals for its versatility and functionality. **

I would like to know if the Casio fx 991ES calculator has the ability to perform complex calculations such as matrix operations, solving equations, and calculus functions. Additionally, I am curious about the user interface and ease of use of the calculator. Finally, I would like to know if there are any unique features or functions that set the Casio fx 991ES apart from other scientific calculators on the market. **

The Casio FX 991ES Plus calculator is a scientific calculator with advanced features, and it is not typically susceptible to hacking in the same way that other electronic devices might be. However, like any electronic device, it is possible for someone with advanced technical knowledge to potentially manipulate or modify the calculator's software or hardware. That being said, the average user would not need to worry about the calculator being hacked in the same way that a computer or smartphone might be. **

To display longer decimal numbers on the Casio fx-991ES, you can adjust the number of decimal places shown by pressing the "MODE" button, then selecting "Fix" or "Sci" for fixed or scientific notation. In "Fix" mode, you can set the number of decimal places you want to display. In "Sci" mode, the calculator will display numbers in scientific notation, showing more decimal places for very large or very small numbers. By adjusting these settings, you can control how many decimal places are displayed on the calculator. **

The "d" in the display of the Casio fx-991ES calculator stands for "decimal." This indicates that the calculator is set to display numbers in decimal format. The calculator also has options to display numbers in other formats such as fraction, scientific notation, and engineering notation. **