Scientific calculator performs 556 scientific functions and features WriteView Technology. With WriteView, the four-line, 12-digit LCD displays a formula exactly the way it is shown in textbooks. Other functions include three-digit punctuation, two variable statistics, six modes (normal, drill, stat, complex, matrix, List, Equation) and fraction calculations. Four programmable keys offer quick access to user functions. Calculator can solve three simultaneous equations and delivers fast calculation speed and smooth operation. The Playback feature allows you to edit and make changes to formulas easily. The hard slide cover protects the calculator so it can withstand frequent use. Calculator is recommended for general math, pre-algebra, algebra, trigonometry, calculus, and biology. PTA approved tests include AP Chemistry, AP Physics, PSAT/NMSQT, SAT I, SAT II, Math IC, and Math IIC. Twin power calculator runs on solar power and battery power.