HP 40gs - Page 236

14-54 Computer Algebra System (CAS)
MULTMOD Performs a multiplication in Z/pZ or in Z/pZ[X].
Example 1
Typing:
MULTMOD(11, 8)
gives:
–3
Example 2
Typing:
MULTMOD(11X + 5, 8X + 6)
gives:
POWMOD Calculates A to the power of N in Z/pZ[X], and A(X) to
the power of N in Z/pZ[X].
Example 1
If p = 13, typing:
POWMOD(11, 195)
gives:
5
In effect: 11
12
= 1 mod 13, so 11
195
= 11
16×12+3
= 5
mod 13.
Example 2
Typing:
POWMOD(2X + 1, 5)
gives:
since 32 = 6 (mod 13), 80 = 2 (mod 13), 40 = 1 (mod
13), 10 = –3 (mod 13).
3x
2
2x–4–()–
6x
5
2x
4
2x
3
x
2
3x–1+++ +
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