HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 212

identical to the first. The original hp 38g only had the, function and

Page 212 highlights

Step 2. Enter the 3x3 matrix of coefficients in M1. Step 3. Enter the 3x1 matrix of into M2. Note the change to in order to make entering numbers easier. Step 4. Change to the HOME view, evaluate A−1 × b using any of the following three methods (all of which are acceptable to the hp 39gs or hp 40gs), and store the result into M3. (a) M1-1*M2 (b) M2/M1 (c) INVERSE(M1)*M2 The best of these is probably the first. The inverse x-1 function is on the keyboard and this makes it more convenient to use. The only problem with the second method is that it does not make it clear that the operation is really left-multiplication by the inverse rather than division, an operation which is not strictly speaking defined for matrices but is allowed for convenience on the calculator. The third option is actually identical to the first. The original hp 38g only had the INVERSE function and the x-1 function was added in later models. They are mathematically identical but the function x-1 can be found on the keyboard and so is simpler to use. The answer displayed is [[2],[-3],[.999999999999]]. This is really the same as x = 2, y = -3, z = 1. The strange answer for z = 1 is caused by internal precision errors. You are expected to realize yourself that it should be z = 1. 212

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Step 2. Enter the 3x3 matrix of coefficients in
M1
.
Step 3. Enter the 3x1 matrix of into
M2
.
Note the change to
in order to make entering numbers
easier.
1
Step 4. Change to the
HOME
view, evaluate
A
×
b
using any of the
following three methods (all of which are acceptable to the
hp 39gs or hp 40gs), and store the result into
M3
.
(a)
M1
-1
*M2
(b)
M2/M1
(c)
INVERSE(M1)*M2
The best of these is probably the first.
The inverse
x
-1
function is on the keyboard and this makes it more
convenient to use.
The only problem with the second method is that it does not make it clear that the
operation is really left-multiplication by the inverse rather than division, an operation which is not strictly
speaking defined for matrices but is allowed for convenience on the calculator. The third option is actually
identical to the first. The original hp 38g only had the
INVERSE
function and the
x
-1
function was added in
later models. They are mathematically identical but the function
x
-1
can be found on the keyboard and so is
simpler to use.
The answer displayed is
[[2],[-3],[.999999999999]].
This is really the same as
x = 2, y = -3, z = 1.
The
strange answer for z = 1 is caused by internal precision errors. You are expected to realize yourself that it
should be z = 1.
212