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\(\left[8x-120:4\right]\times3^3=3^6.\)
\(8x-120:4=3^3\)
\(8x-30=27\)
\(8x=27+30\)
\(8x=57\)
\(x=19\)
123 - 5.(x + 4) = 38
123 - 5x - 20 = 38
-5x = 38 - 123 + 20
-5x = -65
x = -65 : -5
x = 13
Vậy x = 13
( 3 x ( x + 2 ) : 7 ) x 4 = 120
( 3 x ( x + 2 ) : 7 ) = 120 : 4
3 x ( x + 2 ) : 7 = 30
3 x ( x + 2 ) = 30 x 7
3 x ( x +2 ) = 210
x + 2 = 210 : 3
x + 2 = 70
x = 68
275-(113+x)+63=158
275-(113+x)=95
113+x=175-95
113+x=80
x=80-113
x=33
[3(x+2):7]4=120
3(x+2):7=30
3(x+2)=210
x+2=70
x=68
\(\Leftrightarrow3\left(x+2\right):7=30\)
=>3(x+2)=210
=>x+2=70
hay x=68
\(\left[3\cdot\left(x+2\right)\div7\right]\cdot4=120\)
\(3\cdot\left(x+2\right)\div7=120\div4\)
\(3\cdot\left(x+2\right)\div7=30\)
\(3\left(x+2\right)=30\cdot7\)
\(3\cdot\left(x+2\right)=210\)
x+2=210:3
x+2=70
x=68
a) \(\left(x-1\right)^3=8=2^3\)
\(x-1=2\)
\(x=2+1=3\)
b) \(7^{2x-6}=49=7^2\)
\(2x-6=2\)
\(2x=6+2=8\)
\(x=8:2=4\)
c) \(\left(2x-14\right)^7=128=2^7\)
\(2x-14=2\)
\(2x=14+2=16\)
\(x=16:2=8\)
d) \(x^4\cdot x^5=5^3\cdot5^6=5^4\cdot5^5\)
\(x=5\)
e) \(3\cdot\left(x+2\right):7\cdot4=120\)
\(x+2=120:3\cdot7:4\)
\(x+2=70\)
\(x=70-2=68\)
Lời giải:
a. $(x-1)^3=8=2^3$
$\Rightarrow x-1=2$
$\Rightarrow x=3$
b. $7^{2x-6}=49=7^2$
$\Rightarrow 2x-6=2$
$\Rightarrow 2x=8$
$\Rightarrow x=4$
c. $(2x-14)^7=128=2^7$
$\Rightarrow 2x-14=2$
$\Rightarrow 2x=16$
$\Rightarrow x=18$
d.
$x^4.x^5=5^3.5^6$
$x^9=5^9$
$\Rightarrow x=5$
e.
$3(x+2):7=120:4=30$
$3(x+2)=30.7=210$
$x+2=210:3=70$
$x=70-2=68$
a,x-6/7=5/2
x=5/2+6/7
x=47/14
b,12/7:x+2/3=7/5
12/7:x=7/5-2/3
12/7:x=11/15
x=12/7:11/15
x=180/77
c,2/3.x+3/4=3
2/3.x=3-3/4
2/3.x=9/4
x=9/4:2/3
x=27/8
d,720:[41-(2x-5)]=120
[41-(2x-5)]=720:120
[41-(2x-5)]=6
(2x-5)=41-6
(2x-5)=35
2x=35+5
2x=40
x=40:2
x=20
\(\left[3\cdot\left(x+2\right):7\right]\cdot4=120\)
\(\Rightarrow3\left(x+2\right):7=30\)
\(\Rightarrow3\left(x+2\right)=210\)
\(\Rightarrow x+2=70\)
\(\Rightarrow x=68\)
Vậy x=68
[ 3 . ( x + 2 ) : 7 ] . 4 = 120
3 . ( x + 2 ) : 7 = 30
3 . ( x + 2 ) = 210
x + 2 = 70
x = 68
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