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\(BC\left(12,21,28\right)=B\left(84\right)=\left\{0;84;168;252;336;...\right\}\\ \Rightarrow x\in\left\{168;252\right\}\left(150< x< 300\right)\)
2. Tìm số tự nhiên x , biết:
a) ( 2600 + 6400 ) - 3 . x = 1200
<=> 9000 -3x = 1200
<=> 3x = 9000 - 1200
<=> 3x = 7800
=> x = 7800 : 3
=> x = 2600
1: =>5(2x+6)=40
=>2x+6=8
=>2x=2
=>x=1
2: =>12-(x+3)=256:64=4
=>(x+3)=8
=>x=5
3: =>2x-1=3 hoặc 2x-1=-3
=>x=2 hoặc x=-1
4: \(\Leftrightarrow3^{x+2017}=3^{2015}\)
=>x+2017=2015
=>x=-2
a)
720 : (x - 17) = 12
x – 17 = 60
x = 60 + 17
x = 77
b)
(x - 28) : 12 = 8
x – 28 = 8 . 12
x – 28 = 96
x = 124
c)
26 + 8x = 6x + 46
8x – 6x = 46 – 26
2x == 20
x = 10
d)
3600 : [(5x + 335) : x] = 50
(5x + 335) : x = 72
5x + 335 = 72x
67x = 335
x = 5
\(a,Ư\left(84\right)=\left\{1;2;3;4;6;7;12;14;21;28;42;84\right\}\\ \Rightarrow x\in\left\{7;12;14;21;28;42;84\right\}\\ b,B\left(12\right)=\left\{0;12;24;36;48;60;..\right\}\\ \Rightarrow x\in\left\{0;12;24;36;48\right\}\\ c,BC\left(28,56,70\right)=B\left(280\right)=\left\{0;280;560;840;...\right\}\\ \Rightarrow x=560\)
a,Ư(84)={1;2;3;4;6;7;12;14;21;28;42;84}
⇒x∈{7;12;14;21;28;42;84}
b,B(12)={0;12;24;36;48;60;..}
⇒x∈{0;12;24;36;48}
c,BC(28,56,70)=B(280)={0;280;560;840;...}
⇒x=560
\(x-\left[42+\left(-28\right)\right]=-8\)
\(x-\left[42-28\right]=-8\)
\(x-14=-8\)
\(x=-8+14\)
\(x=-8-\left(-14\right)\)
\(x=6\)
x=(42+(-28)=-8
x=(42-28)=-8
x=14-8
=8+14
x=8-14
x=6