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a) \(6-2\left(x+4\right)=-4\)
\(\Leftrightarrow6-2x-8=-4\)
\(\Leftrightarrow-2-2x=-4\)
\(\Leftrightarrow-2x=-4+2\)
\(\Leftrightarrow-2x=-2\)
\(\Leftrightarrow x=1\)
Vậy \(x=1\)
b) tự làm.
c) \(2x-15:5=-7\)
\(\Leftrightarrow2x-7,5=-7\)
\(\Leftrightarrow2x=-7+7,5\)
\(\Leftrightarrow2x=0,5\)
\(\Leftrightarrow x=0,25\)
\(\Leftrightarrow x=\dfrac{1}{4}\)
Vậy \(x=\dfrac{1}{4}\)
d) \(231-\left(x-6\right)=1339:13\)
\(\Leftrightarrow231-x+6=103\)
\(\Leftrightarrow237-x=103\)
\(\Leftrightarrow237-x+6=103\)
\(\Leftrightarrow-x=103-237\)
\(\Leftrightarrow-x=-134\)
\(\Leftrightarrow x=134\)
e) đề j mà có 2 dấu bằng >> sai :v
f) \(28-x^3=1\)
\(\Leftrightarrow-x^3=1-28\)
\(\Leftrightarrow-x^3=-27\)
\(\Leftrightarrow x^3=27\)
\(\Leftrightarrow x^3=3^3\)
\(\Leftrightarrow x=3\)
Vậy \(x=3\)
g) \(\left(x+2\right)^3=27\)
\(\Leftrightarrow\left(x+2\right)^3=3^3\)
\(\Leftrightarrow x+2=3\)
\(\Leftrightarrow x=3-2\)
\(\Leftrightarrow x=1\)
Vậy \(x=1\)
h) \(81-\left(x-5\right)^2=56\)
\(\Leftrightarrow-\left(x-5\right)^2=56-81\)
\(\Leftrightarrow-\left(x-5\right)^2=-25\)
\(\Leftrightarrow\left(x-5\right)^2=25\)
\(\Leftrightarrow x-5=\pm5\)
\(\Leftrightarrow\left[{}\begin{matrix}x-5=5\\x-5=-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5+5\\x=-5+5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=10\\x=0\end{matrix}\right.\)
Vậy \(x_1=0;x_2=10\)
j) \(x^2=9\)
\(\Leftrightarrow x=\pm3\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)
Vậy \(x_1=-3;x_2=3\)
l) tự làm.
\(a.2.x-138=2^3.3^2\)
\(2.x-138=8.9\)
\(2.x-138=72\)
\(2.x\) \(=72+138\)
\(2.x\) \(=210\)
\(x\) \(=210:2\)
\(x\) \(=105\)
\(b.231-\left(x-6\right)=1339:13\)
\(231-\left(x-6\right)=103\)
\(x-6=231-103\)
\(x-6=128\)
\(x\) \(=128+6\)
\(x\) \(=134\)
\(c.\left[\left(6.x-72\right):2-84\right].28=5628\)
\(\left[\left(6.x-72\right):2-84\right]\) \(=5628:28\)
\(\left(6.x-72\right):2-84\) \(=201\)
\(\left(6.x-72\right):2\) \(=201-84\)
\(\left(6.x-72\right):2\) \(=117\)
\(6.x-72\) \(=117.2\)
\(6.x-72\) \(=234\)
\(6.x\) \(=234+72\)
\(6.x\) \(=306\)
\(x\) \(=306:6\)
\(x\) \(=51\)
mik nè
1/ -7264 + (1543 + 7264)
=-7264 + 1543 + 7264=1543
2/ (144 – 97) – 144
=144-97-144=-97
3/ (-145) – (18 – 145)(Vì có dấu trừ ở trước ngoặc nên p đổi dấu)
=-145-18+145=-18
4/ 111 + (-11 + 27)
=111-11+27=137
I love you
a,231 - ( x - 6 ) = 1339 : 13
=> 231 - ( x - 6 ) = 103
=> x = 6 + 231 - 103
=> x = 1 34
b,
( 3x - 21 ) : 4 + 108 = 144
=> ( 3x - 21 ) : 4 = 144 - 108
=> ( 3x - 21 ) :4 = 36
=> 3x - 21 = 36.4
=> 3x - 21 = 144
=> 3x = 144 + 21
=> 3x = 165
=> x = 165 : 3
=> x = 55
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