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a)3 . 103 + 2 . 102 + 5 . 10
= 3 . 102 . 10 + 2 . 10 . 10 + 5 . 10
= 10 . ( 3 . 102 + 2 . 10 + 5 )
= 10 . ( 3 . 100 + 20 + 5 )
= 10 . ( 300 + 20 + 5 )
= 10 . 325
= 3250
a) 3 . 103 + 2 . 102 + 5 . 10
= 3 . 1000 + 2 . 100 + 5 . 10
= 3000 + 200 + 50
= 3250
a: \(A=25+125=150\)
b: \(B=16+64=80\)
c: \(C=32+9+1=33+9=42\)
d: \(D=1+8+27=35+1=36\)
g: \(K=11\cdot3^{29}-\dfrac{3^{30}}{4\cdot3^{28}}=11\cdot3^{29}-\dfrac{9}{4}\)
1) 279 : 81 = (33)9 : 34 = 327 : 34 = 323
2) a) = 170.3 + 154 : 14 = 510 + 11 = 521
b) = 136.(25 + 75) - 72 = 13600 - 49 = 13 551
c) = (2.5)3 - [(7.2)3 - 25.(64: 8 + 121 : 121 - 2.2)] = 1000 - [2744 - 25.(8 + 1 - 4)] = 1000 - 2619 = 1619
b) 3^2 . [(5^2 - 3 ) : 11 ] - 2^4 + 2.10^3
= 9 . [(25 - 3 ) : 11 ] - 16 + 2.1000
= 9 . [22 : 11 ] - 16 + 2000
= 9 . 2 - 16 + 2000
= 18 - 16 + 2000
= 2 + 2000
= 2002
(72005 + 72004) : 72004
= 72005 : 72004 + 72004 : 72004
= 72005 - 2004 + 1
= 71 + 1
= 7 + 1
= 8
a) ( 3^5 . 3^7 ) : 3^10 + 5.2^4 - 7^3 : 7
= 3^10 : 3^10 + 80 - 7^2
= 1 + 80 - 49
= 32
Bài 3 :
a) \(1+\left(-2\right)+3+\left(-4\right)+...+19+\left(-20\right)\)\(=\left[1+\left(-2\right)\right]+\left[3+\left(-4\right)\right]+...+\left[19+\left(-20\right)\right]\)
\(=\left(-1\right)+\left(-1\right)+...+\left(-1\right)\)
\(=\left(-1\right)\cdot10=-10\)
b) \(1-2+3-4+...+99-100=\left(1-2\right)+\left(3-4\right)+...+\left(99-100\right)\)
\(=\left(-1\right)+\left(-1\right)+...+\left(-1\right)\)
\(=\left(-1\right)\cdot50=-50\)
c) \(2-4+6-8+...+46-48+50-52=\left(2-4\right)+\left(6-8\right)+...+\left(50-52\right)\)
\(=\left(-2\right)+\left(-2\right)+...+\left(-2\right)\)
\(=\left(-2\right)\cdot13=-26\)
d) \(-1+3-5+7-...-97+99\)\(=\left(-1+3\right)+\left(-5+7\right)+...+\left(-97+99\right)\)
\(=2+2+...+2\)
\(=2\cdot25=50\)
e) \(1+\left(-2\right)+3+\left(-4\right)+...+1999+\left(-2000\right)+2001\)\(=\left[1+\left(-2\right)\right]+\left[3+\left(-4\right)\right]+...+\left[1999+\left(-2000\right)\right]+2001\)
\(=\left(-1\right)+\left(-1\right)+...+\left(-1\right)+2001\)
\(=\left(-1\right)\cdot1000+2001=-1000+2001=1001\)
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Bài 4 :
a) \(\left(2ab^2\right):\left(abc\right)=\left[2\cdot4\cdot\left(-6^2\right)\right]:\left[4\cdot\left(-6\right)\cdot12\right]\)
\(=\left[2\cdot4\cdot36\right]:\left[4\cdot\left(-6\right)\cdot12\right]\)
\(=\left[8\cdot36\right]:\left[-24\cdot12\right]\)
\(=288:\left(-288\right)=-1\)
b) \(\left[\left(-25\right)\cdot\left(-27\right)\cdot\left(-x\right)\right]:y=\left[\left(-25\right)\cdot\left(-27\right)\cdot4\right]:\left(-9\right)\)
\(=\left[675\cdot4\right]:\left(-9\right)=2700:\left(-9\right)=-300\)
c) \(\left(a^2-b^2\right):\left(a+b\right)\left(a-b\right)=\left(5^2-\left(-3^2\right)\right):\left(5+\left(-3\right)\right)\left(5-\left(-3\right)\right)\)
\(=\left(25-9\right):\left(5+\left(-3\right)\right)\left(5-\left(-3\right)\right)\)
\(=16:2\cdot8=8\cdot8=64\)
a/ 35 – 2.1111 + 3. 72
= 35 - 2.1 + 3.49
= 35 - 2 + 147
= 33 + 147
= 180
b/ 5.43 + 2.3 – 81. 2 + 7
= 5.64 + 6 - 162 + 7
= 320 + 6 - 162 + 7
= 326 - 162 + 7
= 164 + 7
= 171
c/ 25 + 2.{12 + 2.[3.(5-2)+1]+1}+1
= 32 + 2.{12 + 2.[3.3+1]+1}+1
= 32 + 2.{12 + 2.10+1}+1
= 32 + 2.{12 + 20 + 1}+1
= 32 + 2.{32+1}+1
= 32 + 2.33 + 1
= 32 + 66 + 1
= 98 + 1
= 99
d/ 17.131 + 69.17
= 17 . (131+69)
= 17 . 200
= 3400
e/ 50 – [30 - (6 - 2)2 ]
= 50 - [30 - 42]
= 50 - 14
= 36
f/ 199 +36 + 201 + 184 + 37
= (199+201)+(36+184)+37
= 400 + 220 + 37
= 657
:O