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help for solvcui, solvqui                             (Author:  David Harrison)
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Find real roots of cubic and quadratic polynomials

solvcui a b c d

solvcui e f g

solvqui a b c

Description

solvcui finds the real roots of a cubic polynomial of the form

ax³ + bx² + cx + d = 0 (first syntax)

or

x³ + ex² + fx + g = 0 (second syntax)

solvqui finds the real roots of a quadratic polynomial of the form

ax² + bx + c = 0

Both commands use formulae designed to minimize roundoff error. No output is displayed to the screen, but the roots are returned as scalars in ascending order in r(x1), r(x2) and (for solvcui) r(x3); see help return. Complex roots return missing. The commands are immediate, all their arguments are numbers; see help immed.

Examples

. solvcui 2 -7 7 -2

. solvcui -6 11 -6

. solvqui 1 -9 20

Maintainer

David A. Harrison Intensive Care National Audit & Research Centre david@icnarc.org

Also see

Online: help for return, immed