HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 203

POLYFORM(,) This is a very powerful and useful polynomial function. It allows algebraic manipulation and expansion of an expression into a polynomial. The expected parameters for the function are firstly the expression to be expanded, and secondly the variable which is to be the subject of the resulting polynomial. If the expression contains more than one variable then any others are treated as constants. Eg. 1 Expand (2x − 3)3 ( x −1)2 Result: 8x5 − 52x4 +134x3 −171x2 +108x − 27 The resulting polynomial is shown both as it appears in the HOME view and as it appears after pressing the key. Once it appears in the window, of course, it can be scrolled right and left to see the missing terms. Eg. 2 Expand (3a − 2b)4 This function contains two variables, A and B, which must be expanded separately. The first expansion, treating A as the variable, is done using the expression POLYFORM((3A-2B)^4,A). As you can see if you examine the view after pressing , the expansion of the expression in terms of A has been done, but the terms involving B are not fully evaluated. The solution to this is to use POLYFORM again. Use the MATH menu to fetch the POLYFORM function to the edit line, then move the cursor up to the partially evaluated expression that was the result of the previous POLYFORM. Copy it into the edit line and add a comma, a B and an end bracket. Pressing ENTER will now evaluate the terms involving B. After pressing ENTER the for the second evaluation, the result is shown right (after pressing ). 203