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a/ 440 + 2 [ 125 - x ] = 546
==> 2 [ 125 - x ] = 546 - 440
==> 2 [ 125 - x ] 106
==> 125 - x = 106 : 2
==> 125 - x = 53 ==> x = 125 - 53 =72
b/ 7x - 33 = 27 : 24
==> 7x - 27 = 27-4 = 23 = 8
==> 7x = 8+ 27
==> 7x = 35 ==> x = 35 : 7 = 5
c/ [ 12x - 43 ] . 83 = 4 . 84
==> [ 12x - 26 ] . 29 = 22 . 212
==> [ 12x - 26 ] . 29 = 214
==> [ 12x - 26 ] = 214 : 29 = 25
==>. 12x = 25 + 26 = 96
==> x = 96 : 12 = 8
d/ 123 - 5. [ x + 4 ] = 38
==> 5. [ x + 4 ] = 123 - 38
==> 5. [ x + 4 ] = 85
==> x + 4 = 85 : 5
==> x + 4 = 17
==> x = 17 - 4 = 13
e/ [ 2600 + 6400 ] - 3.x = 1200
==> 9000 - 3x = 1200
==> 3x = 9000 -1200 = 7800
==> x = 7800 : 3 = 2600
f/ x2 - 72 : 36 = 23
==> x2 - 2 = 23
==> x2 = 23 + 2
==>x2 = 25
==> x2 = 52
==> x = 5
5^6+5^7+5^8
=5^6.(1+5+5^2)
=5^6.31 chia hết cho 31
7^6+7^5-7^4
=7^4.(7^2+7-1)
=7^4.55 chia hết cho 11
BÀI 2:
a) \(5^6+5^7+5^8=5^6\left(1+5+5^2\right)=5^6.31\) \(⋮\)\(31\)
b) \(7^6+7^5-7^4=7^4.\left(7^2+7-1\right)=7^4.55\)\(⋮\)\(11\)
c) \(2^3+2^4+2^5=2^3.\left(1+2+2^2\right)=2^3.7\)\(⋮\)\(7\)
d) mk chỉnh đề
\(1+2+2^2+2^3+...+2^{59}\)
\(=\left(1+2\right)+\left(2^2+2^3\right)+...+\left(2^{58}+2^{59}\right)\)
\(=\left(1+2\right)+2^2\left(1+2\right)+...+2^{58}\left(1+2\right)\)
\(=\left(1+2\right)\left(1+2^2+...+2^{58}\right)\)
\(=3\left(1+2^2+...+2^{58}\right)\)\(⋮\)\(3\)
1) 5(x - 2) + 27 = 4x - 8
=> 5x - 10 + 27 = 4x - 8
=> 5x + 17 = 4x - 8
=> 5x - 4x = -8 - 17
=> x = -25
2) 3(x + 1) + 2(x + 2) = -13
=> 3x + 3 + 2x + 4 = -13
=> 5x + 7 = -13
=> 5x = -13 - 7
=> 5x = -20
=> x = -20 : 5
=> x = -4
3) (2x + 4)(5 - x) = 0
=> \(\orbr{\begin{cases}2x+4=0\\5-x=0\end{cases}}\)
=> \(\orbr{\begin{cases}2x=-4\\x=5\end{cases}}\)
=> \(\orbr{\begin{cases}x=-2\\x=5\end{cases}}\)
Vậy ...
4) x2 - 3x = 0
=> x(x - 3) = 0
=> \(\orbr{\begin{cases}x=0\\x-3=0\end{cases}}\)
=> \(\orbr{\begin{cases}x=0\\x=3\end{cases}}\)
Vậy ...
5) x2 - 3x + 2 = 0
=> x(x - 3) = -2
=> x(x - 3) = 1 . (1 - 3)
=> x = 1
a) \(63^7< 64^7=\left(2^6\right)^7=2^{42}< 2^{48}=\left(2^4\right)^{12}=16^{12}\Rightarrow63^7< 16^{12}\)
b) \(3^{151}>3^{150}=\left(3^2\right)^{75}=9^{75}>8^{75}=\left(2^3\right)^{75}=2^{225}\)
c) \(9^{20}=\left(3^2\right)^{20}=3^{40}>3^{39}=\left(3^3\right)^{13}=27^{13}\Rightarrow9^{20}>27^{13}\)
bài 2:
a)\(2^x=32\Leftrightarrow2^x=2^5\Leftrightarrow x=5\)
b)\(2x+3^4=7^2\Leftrightarrow2x+81=49\Leftrightarrow2x=-32\Leftrightarrow x=-16\)
c)\(12x-33=3^2\Leftrightarrow12x-33=9\Leftrightarrow12x=42\Leftrightarrow x=\frac{7}{2}\)
Bài làm
a) 200 - ( 2x + 6 ) = 43 b) 32 ( x + 4 ) - 52 = 5.22
2x + 6 = 200 - 64 32 ( x + 4 ) = 20 + 25
2x + 6 = 136 32 ( x + 4 ) = 45
2x = 136 - 6 x + 4 = 45 : 9 (chỗ này là x + 4 = 45 : 32 )
2x = 130 x + 4 = 5
x = 130 : 2 x = 5 - 4
x = 65 x = 1
Vậy x = 65 Vậy x = 1
c) ( x - 36 ) : 18 = 12 d) ( x - 47 ) - 115 = 0
x - 36 = 12 * 18 x - 47 = 115
x - 36 = 216 x = 115 + 47
x = 216 + 36 x = 162
x = 252 Vậy x = 162
Vậy x = 252
e) 0 : x = 0 f) 3x = 9
Vì 0 : x = 0 => 3x = 32
=> \(\frac{0}{x}=0\) => x = 2
Mà số 0 không bao giờ ở mẫu số. Vậy x = 2
=> \(x\in\left\{N\right\}\)
Vậy \(x\in\left\{N\right\}\)
g) 4x = 64
=> 4x = 43
=> x = 3
Vậy x = 3
# Chúc bạn học tốt #
1) \(\frac{1}{9}\times27^n=3^n\)
\(\Rightarrow\frac{1}{3^2}\times\left(3^3\right)^n=3^n\)
\(\Rightarrow3^{-2}\times3^{3n}=3^n\)
\(\Rightarrow3^{-2+3n}=3^n\)
\(\Rightarrow-2+3n=n\)
\(\Rightarrow2n=2\)
\(\Rightarrow n=1\)
2) \(32< 2^n< 128\)
\(\Rightarrow2^5< 2^n< 2^7\)
\(\Rightarrow5< n< 7\)
\(\Rightarrow n=6\)
3) \(2\times16\ge2^n>4\)
\(\Rightarrow32\ge2^n>4\)
\(\Rightarrow2^5\ge2^n>2^2\)
\(\Rightarrow\)\(5\ge n>2\)
\(\Rightarrow n\in\left\{5;4;3\right\}\)
12 + 22 + 33
= 1 + 4 + 27
= 5 + 27
= 32
( 24 + 32 ) : 2
= ( 16 + 9 ) : 2
= 25 : 2
= 12,5
~ Hok tốt ~
\(1)\)
\(-3-18\)
\(=-(3+18)\)
\(=-21\)
\(-7\times-5\)
\(=7\times(-1)\times(-5)\)
\(=7\times5\)
\(=35\)
\(5+(-11)\)
\(=5-11\)
\(=-6\)
1,
a) -3 - 18=-21
b) (-7).(-5)=35
c) 5+(-11)=-6
2,
a) -2-13+(-14)-19=-48
b) 221 + 4[(-5).8-4]=45
c) (-2)3.(-2)2+32=0
d) -15.12 - 8.(-12)=-84
3,
a) x:(-2)=9
=>x =9.(-2)
=>x =-18
b)4x+(-8)=24
=>4x =24-(-8)
=>4x =32
=>x =32:4
=>x =8
c) (3x)(x+7)=0
\(\Rightarrow\hept{\begin{cases}3x=0\\x+7=0\end{cases}\Rightarrow\hept{\begin{cases}x=0:3\\x=0-7\end{cases}\Rightarrow}\hept{\begin{cases}x=0\\x=-7\end{cases}}}\)
b) 60 : x - 2 = 30
= 60 : x = 30 + 2
= 60 : x = 32
= x = 60 : 32
= x = 1,875
c) x : 4 + 1 = 3
= x : 4 = 3-1
= x : 4 = 2
= x = 2x 4
= x = 8
d) ( x - 13 ) = 8
= x - 1 = 8
= x = 8+1
= x = 9
e) 3 x - 2 = 27
= 3x : 32 = 27
= 3x : 9 = 27
= 3x = 27x9
= 3x = 243
= 3x = 35
= x = 5