HP 40gs User Manual page 217

hp40g+.book Page 35 Friday, December 9, 2005 1:03 AM
LDEC
LINSOLVE
Computer Algebra System (CAS)
Linear differential equations having constant
coefficients
LDEC enables you to directly solve linear differential
equations having constant coefficients.
The parameters are the second member and the
characteristic equation.
Solve:
y" − 6 · y' + 9 · y = x · e
Typing:
LDEC(X·EXP(3·X),X
gives:
( ⋅ ) cC0 ⋅
18 x 6 – –
⎛
---------------------------------------------------------------------------------------- -
-
⎝
6
cC0 and cC1 are integration constants (y(0) = cC0 and
y'(0) = cC1).
Solve linear system
LINSOLVE enables you to solve a system of linear
equations.
It is assumed that the various equations are of the form
expression = 0.
LINSOLVE has two arguments: the first members of the
various equations separated by AND, and the names of
the various variables separated by AND.
Example 1
Typing:
LINSOLVE(X+Y+3 AND X-Y+1, X AND Y)
gives:
(x = −2) AND (y = −1)
or, in Step-by-step mode (CFG, etc.):
L2=L2−L1
1 1 3
–
1 1 1
ENTER
3·x
2
−6·X+9)
3
( ⋅ ⋅ )
6 x cC1 + x
⋅ ( 3 x ⋅
exp
⎞
)
⎠
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