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a: =>31-x=60
=>x=-29
b: =>(x-140):35=280-270=10
=>x-140=350
=>x=490
c: =>(1900-2x):35=48
=>1900-2x=1680
=>2x=220
=>x=110
d: =>\(2^{2x-1}=2^9\cdot2=2^{11}\)
=>2x-1=11
=>x=6
e: =>(x+2)^5=4^5
=>x+2=4
=>x=2
f: =>3x-4=0 hoặc x-1=0
=>x=4/3 hoặc x=1
g: =>(2x-1)^2=49
=>2x-1=7 hoặc 2x-1=-7
=>x=-3 hoặc x=4
h: =>x(x+1)/2=78
=>x(x+1)=156
=>x=12
a) (x - 78) .26 = 0 => x - 78 = 0 => x = 78
b) 39 (x - 5) = 39 => x - 5 = 1 => x = 6
c) (x - 14) : 2 = 3 => x - 14 = 6 => x = 20
d) (30 - x) . 4 = 92
=> 30 - x = 92 : 4
=> 30 - x = 23
=> x = 30 - 23 = 7
e) 45(91 - x) = 90
=> 91 - x = 90 : 45
=> 91 - x = 2
=> x = 91 - 2 = 89
f) (2x - 6)(3x - 18) = 0
=> \(\orbr{\begin{cases}2x-6=0\\3x-18=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=3\\x=6\end{cases}}\)
g) 5x + 73.21 = 73.26
=> 5x = 73.26 - 73.21
=> 5x = 73(26 - 21) = 73.5
=> x = \(\frac{73\cdot5}{5}=73\)
h) 2x - 12 - x = 0
=> 2x - x - 12 = 0
=> x - 12 = 0
=> x = 12
a) \(39\times118+29\times82\)
\(=39\times2\times59+29\times2\times41\)
\(=2\times\left(39\times59+29\times41\right)\)
\(=2\times\left(2301+1189\right)\)
\(=2\times3490\)
\(=6980\)
b) \(37\times39+78\times14-13\times85-52\times55\)
\(=37\times3\times13+6\times13\times14+13\times85-4\times13\times55\)
\(=13\times\left(37\times3+6\times14+85-4\times55\right)\)
\(=13\times\left(111+84+85-220\right)\)
\(=13\times\left(280-220\right)\)
\(=13\times60\)
\(=780\)
c) \(368:16+752:16+480:16\)
\(=\left(368+752+480\right):16\)
\(=\left(1120+480\right):16\)
\(=1600:16\)
\(=100\)
d) \(5\times11\times18+9\times31\times10+4\times29\times45\)
\(=5\times11\times9\times2+9\times31\times10+2\times2\times29\times5\times9\)
\(=10\times9\times11+10\times9\times31+10\times29\times2\times9\)
\(=90\times11+90\times31+90\times29\times2\)
\(=90\times\left(11+31+29\times2\right)\)
\(=90\times\left(42+58\right)\)
\(=90\times100\)
\(=9000\)
a) (x - 78) . 26 = 40
=>x-78 = 40 : 26 = 20/13
=> x = 78 + 20/13
=> x = 1034/13
b) 39 . (x-5) =39
=>x-5=39:39=1
=>x=1+5=6
c) 30- ( 52 - x) =90
=>30-52+x=90
=>-22+x=90
=>x=90-(-22)
=>x=112
d) (x-12) : 5 =2
=>x-12=2.5=10
=>x=10+12=22
a, (x-78).26=40
=> (x-78)=40:26
=> x-78=40/26
=> x=40/26+78
=> x=1034/13
b, 39.(x-5)=39
=> x-5=39:39
=> x-5=1
=> x=1+5
=> x=6
c, 30-(52-x)=90
=> 52-x=30-90
=> 52-x=-60
=> x=52-(-60)
=> x=112
d, (x-12):5=2
=> x-12=2.5
=> x-12=10
=> x=10+12
=> x=22