
Press RS, then EQN and display the desired equation.

Press RS, then SOLVE, then press the key for the unknown variable. For example, press RS, SOLVE, then X to solve the variable for x. The equation then prompts for a value for every other variable in the equation.

For each prompt, enter the desired value:

If the displayed value is the one desired, press R/S

If a different value is desired, type or calculate the value and press R/S
Pressing C or R/S can halt a running calculation
When the root is found, it is stored in the unknown variable, and the variable value is viewed in the display. In addition, the Xregister contains the root, the Yregister contains the previous estimate, and the Zregister contains the value of the equation at the root (which should be zero).
For some complicated mathematical conditions, a definitive solution cannot be found and the calculator displays "NO ROOT FOUND". The following conditions cause the message "NO ROOT FOUND":

The search terminates near a local minimum or maximum. If the ending value of f (x) (stored in the Zregister) is relatively close to zero, it is possible that a root has been found; the number stored in the unknown variable might be a 12digit number very close to a theoretical root.

The search halts because Solve is working on a horizontal asymptote  an area where f (x) is essentially constant for a wide range of X. The ending value of f (x) is the value of the potential asymptote.

The search is concentrated in a local "flat' region of the function. The ending value of f (x) is the value of the function in this region.
For certain equations, it helps to provide one or two initial guesses for the unknown variable before solving the equation. This can speed up the calculation, direct the answer toward a realistic solution, and find more than one solution, if appropriate.