Product Description The FX-991ES Plus 2 is an ideal high school and college science calculator with a natural "Textbook" display for displaying formulas and results like a textbook. Suitable for maturity. Equipped with 417 functions including: precision of equations, tuning values, indices of variance, bulk arithmetic, transients, regression and relation coefficients, complex numbers, calcium key (temporary memory combinations), 40 physical invariances, integral and differential numerical arithmetic. Built-in power supply: solar button battery and LR-44.