HP HP-20S - Page 103

Remarks:
If the determinant equals zero, the system of equations is linearly de-
pendent, and this program cannot be used to find a solution. The
message Error - Func will appear if you attempt to solve for x;, x,, or
X3.
To solve two equations in two unknowns, the last column and row of
A should be set to 0 0 1, and the last element of B should be set to 0.
The resulting system of three equations and three unknowns can be
solved as indicated in the program instructions.
When calculating the system solution, no operations are allowed
while the x-values are displayed. If you do any operation other than
(R/S], you must reenter b, and b3 and restart the system solution ac-
cording to step 3 of the program instructions (b, bs A).
If there is a pending expression for by when starting the system solu-
tion ([XEQ] A), it is evaluated before the solution is calculated. If there
is a pending expression when calculating the determinant, the de-
terminant will be calculated incorrectly.
This program uses the following equations:
System of Equations: AX = B
11 A1p Gq3 X1 b,
where A = |a,; a4y, ay|, X =|x|, B =10,
a31 43y 433 X3 b,
Determinant: det A = a,ymn, — asmny; + a,;;mn,
where mn; are the minors mn, = a,,d;3 — 34,3,
mn, = Q33013 — Gql33, M3 = AyA13 — 13053
det, _det, _ det,
/ x2 - / x3 -
det A det A det A
System Solution: x; =
where det; is the determinant of A with its ith column
replaced by B, and det A # 0.
7: Built-in Program Library 101