1.
Chứng minh rằng: D= 777197 - 333163 chia hết cho 10
Chứng minh rằng E= 9931997 - 5571997 chia hết cho 10
2.Tính
a, 50 - [ ( 50-23 . 5 ) : 2 + 3 ]
b, 8697 - [ 37 : 35 + 2 ( 13 - 3 ) ]
c, 205 - [ 1200 - ( 42 - 2. 3 )3 ] : 40
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Bài 1
a, cm : A = 165 + 215 ⋮ 3
A = 165 + 215
A = (24)5 + 215
A = 220 + 215
A = 215.(25 + 1)
A = 215. 33 ⋮ 3 (đpcm)
b,cm : B = 88 + 220 ⋮ 17
B = (23)8 + 220
B = 216 + 220
B = 216.(1 + 24)
B = 216. 17 ⋮ 17 (đpcm)
c, cm: C = 1 - 2 + 22 - 23 + 24 - 25 + 26 -...-22021 + 22022 : 6 dư 1
C=1+(-2+22-23+24- 25+26)+...+(-22017+22018-22019+22020-22021+22022)
C = 1 + 42 +...+ 22016.(-2 + 22 - 23 + 24 - 25 + 26)
C = 1 + 42+...+ 22016.42
C = 1 + 42.(20+...+22016)
42 ⋮ 6 ⇒ C = 1 + 42.(20+...+22016) : 6 dư 1 đpcm
1)
a)251-1
=(23)17-1\(⋮\)23-1=7
Vậy 251-1\(⋮\)7
b)270+370
=(22)35+(32)35\(⋮\)22+32=13
Vậy 270+370\(⋮\)13
c)1719+1917
=(BS18-1)19+(BS18+1)17
=BS18-1+BS18+1
=BS18\(⋮\)18
d)3663-1\(⋮\)35\(⋮\)7
Vậy 3663-1\(⋮\)7
3663-1
=3663+1-2
=BS37-2\(⋮̸\)37
Vậy 3663-1\(⋮̸\)37
e)24n-1
=(24)n-1\(⋮\)24-1=15
Vậy 24n-1\(⋮\)15
\(B=2+2^2+2^3+...+2^{60}\)
\(=2\left(1+2+2^2\right)+...+2^{58}\left(1+2+2^2\right)\)
\(=7\cdot\left(2+...+2^{58}\right)⋮7\)
a, 10615 + 8 không chia hết cho 2 vì 8 ⋮ 2 nhưng 10615 không chia hết cho 2
10615 + 8 không chia hết cho 9 vì 1 + 6 + 1 + 5 + 8 = 21 không chia hết cho 9
c, B = 102010 - 4
10 \(\equiv\) 1 (mod 3)
102010 \(\equiv\) 12010 (mod 3)
4 \(\equiv\) 1(mod 3)
⇒ 102010 - 4 \(\equiv\) 12010 - 1 (mod 3)
⇒ 102010 - 4 \(\equiv\) 0 (mod 3)
⇒ 102010 - 4 \(⋮\) 3
2.
a,\(50-\left[\left(50-2^3.5\right):2+3\right]\)
\(=50-\left[\left(50-40\right):2+3\right]\)
\(=50-\left(10:2+3\right)\)
\(=50-8\)
\(=42\)
b,\(8697-\left[3^7:3^5+2\left(13-3\right)\right]\)
\(=8697-\left(3^2+2.10\right)\)
\(=8697-\left(9+20\right)\)
\(=8697-29\)
\(=8668\)
c,\(205-\left[1200-\left(4^2-2.3\right)^3\right]:40\)
\(=205-200:40\)
\(=200\)
2)
a) \(50-\left[\left(50-2^3.5\right):2+3\right]\)
\(=50-\left[\left(50-8.5\right):2+3\right]\)
\(=50-\left[\left(50-40\right):2+3\right]\)
\(=50-\left(10:2+3\right)\)
\(=50-\left(5+3\right)\)
\(=50-8\)
\(=42\)
b) \(8697-\left[3^7:3^5+2\left(13-3\right)\right]\)
\(=8697-\left(3^7:3^5+2.10\right)\)
\(=8697-\left(3^{7-5}+2.10\right)\)
\(=8697-\left(3^2+2.10\right)\)
\(=8697-\left(9+2.10\right)\)
\(=8697-\left(9+20\right)\)
\(=8697-29\)
\(=8668\)
c) \(205-\left[1200-\left(4^2-2.3\right)^3\right]:40\)
\(=205-\left[1200-\left(16-2.3\right)^3\right]:40\)
\(=205-\left[1200-\left(16-6\right)^3\right]:40\)
\(=205-\left(1200-10^3\right):40\)
\(=205-\left(1200-1000\right):40\)
\(=205-200:40\)
\(=205-5\)
\(=200\)