33
Yechilishi
. Berilgan sonning oxirgi ikki raqami bu sonni 100 ga bo’lganda hosil
bo’ladigan qoldiqdan iborat. Demak, quyidagi taqqoslamani qanoatlantiradigan
x
sonini topish talab qilinadi:
2
100
≡
x
(
mod
100).
Ikkining kichik darajalaridan boshlab, 100 ga bo’lganda hosil bo’ladigan
qoldiqlarni ketma-ket ajratamiz:
2
100
= (2
10
)
10
= (1024)
10
; (1024)
10
≡
(24)
10
(
mod
100).
(24)
10
= (576)
5
≡
76
5
≡
(76)
4
⋅
76 = (5776)
2
⋅
76
≡
(76)
2
⋅
76 = 5776
⋅
76
≡
76
2
≡
5776
≡
76
(
mod
100).
Shunday qilib, 2
100
sonining oxirgi ikki raqamir 7 va 6 dan iborat.
■
5-Misol
.
Agar p – tub son bo’lsa, u holda
k
p
C
1
−
≡
(-1)
k
(mod p)
taqqoslamani
isbotlang.
Yechilishi
. Ma’lumki,
ixtiyoriy
p
va
k
sonlar uchun
k
p
k
p
k
p
C
C
C
=
+
−
−
−
1
1
1
formula
o’rinli,
k
p
C
- butun sondan iborat bo’lib,
p
ga bo’linadi,
chunki
k < p
,
p
esa tub
sondan iborat, shuning uchun u maxrajning birorta ham ko’paytuvchisi bilan qisqarib
ketmaydi. Shunday qilib,
k
p
C
≡
0
(mod p)
. U holda
k
p
C
1
−
≡
(-1)
1
1
−
−
k
p
C
(mod p)
.
Bu rekurrent munosabatni ketma-ket qo’llab, yuqori ko’rsatkichni 1
gacha
kamaytiramiz:
( )
( )
( )
( ) (
) ( ) (
)
p
mo
p
k
k
k
p
k
p
k
p
k
p
C
C
C
C
d
1
1
1
1
1
1
1
3
1
3
2
1
2
1
1
1
−
≡
−
−
≡
≡
−
≡
−
≡
−
≡
−
−
−
−
−
−
−
−
...
.
■
6-Misol
. Agar
a
va
b
– ixtiyoriy butun sonlar,
p
– tub son bo’lsa,
quyidagi
taqqoslamani isbotlang
(a + b)
p
≡
a
p
+ b
p
(mod p)
.
Yechilishi
. Binomni yoyish formulasidan:
p
p
p
p
p
p
p
p
p
p
b
ab
b
a
b
a
a
b)
(a
C
C
C
+
+
+
+
+
=
+
−
−
−
−
1
1
2
2
2
1
1
...
.
O’ng tomonda ikkinchi qo’shiluvchidan boshlab, p
-1
–nchi qo’shiluvchigacha barcha
qo’shiluvchilar
p
ga bo’linadi, chunki
C
k
p
=
k
k
p
p
p
⋅
⋅
⋅
−
−
−
...
2
1
)
1
(
)...(
1
(
, bu yerda
k < p
.
Demak,
(
)
p
d
mo
C
i
p
0
≡
,
i
= 1, 2, ..., (
p
-1).
Bu yerdan
(a + b)
p
≡
a
p
+ b
p
(mod p)
kelib chiqadi.
■
MAShQLAR
1.
Qanday modul bo’yicha barcha butun sonlar o’zaro taqqoslanadi?
2.
Quyidagi taqqoslamalardan qaysilari to’g’ri:
a) 1
≡
-5 (
mod
6); b) 546
≡
0 (
mod
13); c) 1956
≡
5 (
mod
12);
d) 2
3
≡
1 (
mod
4); e) 3
m
≡
-1 (
mod m
)?
3*.
Berilgan modul bo’yicha har qanday butun son o’zining qoldig’i
bilan
taqqoslanishini isbot qiling.
34
n
4n+1
4n+1
4.
Quyidagi taqqoslamalarni qanoatlantiradigan
x
ning
barcha qiymatlarini
toping:
a)
x
≡
0 (
mod
3); b)
x
≡
1 (
mod
2).
5.
Quyidagi taqqoslamalarni qanoatlantiradigan
m
ning barcha qiymatlarini
toping: 3
r
+ 1
≡
r
+ 1 (
mod m
).
6.
Agar
x
= 13 soni
x
≡
5 (
mod m
)
taqqoslamani qanoatlantirsa, modulning
mumkin bo’lgan qiymatlarini toping.
7*.
Agar
n
– toq son bo’lsa,
u holda
n
2
- 1
≡
0 (
mod
8) taqqoslama o’rinli
ekanligini ko’rsating.
8*.
Agar 100
a
+ 10
b
+
c
≡
0 (
mod
21) bo’lsa, u holda
a
– 2
b
+ 4
c
≡
0 (
mod
21) taqqoslamaning o’rinli ekanligini ko’rsating.
9.
Agar 3
n
≡
-1 (
mod
10) bo’lsa, u holda 3
n+4
≡
-1 (
mod
10) (
n
∈
N
)
taqqoslamaning o’rinli ekanligini ko’rsating,.
10*.
2
11
•
31
≡
2 (
mod
11
⋅
31) taqqoslamaning to’g’riligini ko’rsating.
11*.
Agar
x
= 3
n
+ 1,
n
= 0, 1, 2,.... bo’lsa, u holda 1 + 3
x
+ 9
x
ning 13 ga
bo’linishini ko’rsating.
12.
N
= 11
⋅
18
⋅
2322
⋅
13
⋅
19 soni 7 modul bo’yicha absolyut qiymati bo’yicha
eng kichik qanday son bilan taqqoslanadi?
13.
3
14
≡
-1 (
mod
29) ni tekshiring.
14.
1532
5
– 1 ni 9 ga bo’lganda hosil bo’ladigan qoldiqni toping.
15*.
Agar
a
≡
b
(
mod p
n
) bo’lsa, u holda
a
p
≡
b
p
(mod p
n+1
)
ni isbotlang.
16
Agar
ax
≡
bx (mod m)
bo’lsa, u holda
(
)
≡
m
,
x,
m
mo
b
a
d
ni isbotlang.
17*.
Agar
a
4
a
3
a
2
a
1
a
0
≡
0 (
mod
33) bo’lsa, u holda
a
4
+ a
3
a
2
+ a
1
a
0
≡
0 (
mod
33) ni isbotlang. a
i+1
= 0 da
a
i+1
a
i
= a
i
deb oling.
18*.
Berilgan sonning oxirgi ikkita raqamini toping: a) 9
9
; b) 7
9
.
19*.
r
r+
2
+ (
r
+2)
r
≡
0 (
mod
2
r
+2) taqqoslamani isbot qiling, bu yerda
r
> 2.
20*.
Quyidagi sonlarni
,...,
2
3
,
2
1
−
−
−
−
p
p
- 1, 0, 1,...,
2
1
,
2
3
−
−
p
p
r > 2 modul bo’yicha o’zaro taqqoslanmasligini ko’rsating.
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