Casio fx-991ZA Plus User's Guide
![Casio fx-991ZA Plus Calculator manual cover](/images/hGRjsIxSrEAQsSpYDEAAkhZO/thumbs/thumb175x175.webp)
To perform a factory reset, press SHIFT, then 9 (CLR), 3 (All), and finally = (Yes) to reset all settings and clear memory.
Use the MODE button to select EQN (Equation Mode), choose the quadratic equation form, and input the coefficients to find the solutions.
Switch to STAT mode using the MODE button, enter your data points, and use the built-in functions to calculate mean, standard deviation, and other statistical metrics.
Press MODE and select the CMPLX (Complex Number) mode, allowing you to perform calculations with complex numbers.
First, check if the contrast needs adjustment by pressing SHIFT, then SETUP, and using arrow keys to find contrast settings. If the problem persists, consider replacing the battery.
Select MATRIX mode using MODE button, input your matrices, and use the calculator's matrix functions to perform operations like addition, subtraction, and multiplication.
Press the CALC button (∫), input the function and the bounds of integration, then press = to compute the integral.
Press SHIFT, then MODE (SETUP), and select Rad or Deg to switch between radians and degrees.
Utilize the d/dx function by pressing SHIFT and then the CALC button (d/dx). Enter the function and the point of differentiation to calculate the derivative.
Check the battery and replace it if necessary. Ensure the battery is inserted correctly and the contacts are clean.