a) \(2\left(3x-4\right)=18\Leftrightarrow3x-4=9\)
\(\Leftrightarrow3x=13\Rightarrow x=\frac{13}{3}\)
b) \(\left(105-x\right)\div25=30+1\)
\(\Leftrightarrow105-x=775\)
\(\Leftrightarrow x=-670\)
c) \(2x-138=22.32\)
\(\Leftrightarrow x-69=11.32\)
\(\Leftrightarrow x-69=352\)
\(\Rightarrow x=421\)
d) \(\left(6x-9\right).28=5628\)
\(\Leftrightarrow\left(2x-3\right).84=5628\)
\(\Leftrightarrow2x-3=67\)
\(\Leftrightarrow2x=70\)
\(\Rightarrow x=35\)
e) \(\left(9x+2\right).3=60\)
\(\Leftrightarrow9x+2=20\)
\(\Leftrightarrow9x=18\)
\(\Rightarrow x=2\)
g) \(\left(26-3x\right)\div5+71=75\)\(\Leftrightarrow26-3x=20\)
\(\Leftrightarrow3x=6\)
\(\Rightarrow x=2\)
h) \(5x+1=125\)
\(\Leftrightarrow5x=124\)
\(\Rightarrow x=\frac{124}{5}\)
i) \(\left(x-5\right)\left(2x+8\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-5=0\\2x+8=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=5\\2x=-8\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=5\\x=-4\end{cases}}\)
a) 2 ( 3x - 4 ) = 18
<=> 3x - 4 = 9
<=> 3x = 13
<=> x = \(\frac{13}{3}\)
b) ( 105 - x ) : 25 = 30 + 1
<=> ( 105 - x ) : 25 = 31
<=> 105 - x = 775
<=> x = -670
c) 2x - 138 = 22 . 32
<=> 2x - 138 = 704
<=> 2x = 842
<=> x = 421
a) 2 (3x - 4) = 18
3x - 4 = 18 : 2
3x - 4 = 9
3x = 9 + 4
3x = 13
x =\(\frac{13}{3}\)
b) (105 - x) : 25 = 30 + 1
(105 - x) : 25 = 31
105 - x = 31 . 25
105 - x = 775
=> x = -670
c) 2x - 138 = 22 . 32
2x - 138 = 704
2x = 704 + 138
2x = 842
x = 842 : 2
x = 421
d) (6x - 39) . 28 = 5628
6x - 39 = 5628 : 28
6x - 39 = 201
6x = 201 + 39
6x = 240
x = 40
e) (9x + 2) . 3 = 60
9x + 2 = 60 : 3
9x + 2 = 20
9x = 20 - 2
9x = 18
x = 18 : 2
x = 9
g) (26 - 3x) : 5 + 71 = 75
(26 - 3x) : 5 = 75 - 71
(26 - 3x) : 5 = 4
26 - 3x = 4 . 5
26 - 3x = 20
3x = 26 - 20
3x = 6
x = 6 : 3
x = 2
h) 5x + 1 = 125
5x = 125 - 1
5x = 124
x = 124 : 5
x =\(\frac{124}{5}\)= 24,8
i) (x - 5) (2x + 8) = 0
\(\Rightarrow\orbr{\begin{cases}x-5=0\\2x+8=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=5\\2x=-8\end{cases}\Leftrightarrow}}\orbr{\begin{cases}x=5\\x=-4\end{cases}}\)
Sai thì thôi~
#Học tốt!!!
~NTTH~
a) 2( 3x - 4 ) = 18
<=> 3x - 4 = 9
<=> 3x = 13
<=> x = 13/3
b) ( 105 - x ) : 25 = 30 + 1
<=> ( 105 - x ) : 25 = 31
<=> 105 - x = 775
<=> x = -670
c) 2x - 138 = 22 . 32
<=> 2x - 138 = 704
<=> 2x = 842
<=> x = 421
d) ( 6x - 39 ) . 28 = 5628
<=> 6x - 39 = 201
<=> 6x = 240
<=> x = 40
e) ( 9x + 2 ) . 3 = 60
<=> 9x + 2 = 20
<=> 9x = 18
<=> x = 2
g) ( 26 - 3x ) : 5 + 71 = 75
<=> ( 26 - 3x ) : 5 = 4
<=> 26 - 3x = 20
<=> 3x = 6
<=> x = 2
h) 5x + 1 = 125
<=> 5x = 124
<=> x = 124/5
i) ( x - 5 )( 2x + 8 ) = 0
<=> x - 5 = 0 hoặc 2x + 8 = 0
<=> x = 5 hoặc x = -4