HP 39g hp 39g+ (39g & 40g)_mastering the hp 39g+_English_E_F2224-90010.pdf - Page 257

Eg. Solve x2 − 4x − 5 = 0 Use QUAD(X2-4X-5,X) Answer: (4+S1*6)/2 It is now up to you to interpret this algebraically as: 4±6 x= 2 4+6 4−6 = or 2 2 = 5 or − 1 If you are simply after the roots of the quadratic then it is far better to use the POLYROOT function (page 284). If you would like a solution such as 3 + 5 2 rather than 2.6180 then the advantage of QUAD is that you can COPY the result, edit the line to remove all but the decimal root and square it to find the original discriminant. The QUAD function does have one advantage over other methods, in that it will give a complex number solution to quadratics which have complex roots. This may well make it worth using in problems where a complex answer is acceptable or required. Complex numbers are expressed on the hp 39g+ in the form (a, b) representing a + bi. Thus the answer to the second quadratic shown above would represent −2 ± −112 with the −112 6 written as a complex number. See also: FNROOT, LINEAR? QUOTE(var.name) Intended for use mainly by programmers. Programmers sometimes want to store a function such as X2-4 into one of F1(X)...F9(X) using . It turns out that if you use F1(X2-4) then it won't be entered symbolically. Instead, the contents of X (a number) is entered substituted and the expression evaluated to give a numeric result. The QUOTE function fixes this. For example, QUOTE(X)2-4 F1(X) will ensure a symbolic result. An easier method of storing a function into an aplet in a program is to enclose it in single quotes. For example '(X)2-4' F1(X) would serve the same purpose as QUOTE(X)2-4 F1(X). On the other hand, entering F1('X') will not work but F1(QUOTE(X)) will. See Example 1 on page 217 in the chapter "Programming on the hp 39g+" for an example of use. 257