HP HP-20S - Page 106

D 0.5528 Calculates x;. The : an-
nunciator indicates
that this is the
positive-valued imagi-
nary part of the
complex root.
—0.8333 Displays real part of
play P
complex root.
Remarks:
This program can be used in conjunction with the root finder program
to solve cubic equations. Since a cubic equation always has at least
one real root, the root finder program could be used to find the root.
Then synthetic division could reduce the cubic equation to a qua-
dratic equation, which could then be solved by this program.
The message Error - Func appears if the coefficient of the quadratic
term (a) is zero.
If there is a pending expression when the coefficients a, b, and c are
entered, it is evaluated before the coefficients are saved.
This program uses the following equations:
_
7
Quadratic
Formula:
x
=
__b_M
2a
— 2 _
Real
Roots:
If
—b=>0
x=
b
+Vb
4ac
2a
If
—b
<0
x.=
—b—-bz—4ac
o 2a
r = €
2 ax,
Real Part of Complex Root: r = :2%
:
.
V¥
—
4acl
Imaginary Part of Complex Root: i = >
104 7: Built-in Program Library