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Rin sẽ làm bài 2
a. 4 - 2x = -56
2x = 4 + 56
2x = 60
x = 30
b. -9x + 42 = 66
-9x = 24
x = 24 : -9
x = \(\frac{-24}{9}\)
c. 5 x 1x - 111 = 125
1x - 111 = 25
1x = 136
x = 136
d. (2x +1)2 = 81
(2x +1)2 = 92
=> 2x + 1 = 9
2x = 10
x = 5
\(a,-2.\left(x+7\right)+3.\left(x-2\right)=-2\)
\(-2x-14+3x-6=-2\)
\(x-20=-2\)
\(x=-2+20\)
\(x=18\)
\(b,-7-2x=-37-\left(-26\right)\)
\(-7-2x=-11\)
\(-2x=-11+7\)
\(-2x=-4\)
\(x=2\)
\(c,\left(3x+9\right).\left(11-x\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}3x+9=0\\11-x=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-3\\x=11\end{cases}}}\)
\(\orbr{\begin{cases}3x+9=0\\11-x=0\end{cases}}\Rightarrow\orbr{\begin{cases}3x=-9\\x=11\end{cases}}\Rightarrow\orbr{\begin{cases}x=-3\\x=11\end{cases}}\)
A. 2.9 +6 -4 = 20
B. 8.25 - 6.9 + (-12) = 134
C. -962 + 1548 = 586
D. -85.(36+54) = -85 x 100 = -8500
F. 26.37 - 26.56 - 56.37 + 56.26 =26.37 - 56.37 = 37.(26 - 56)
=37. (-30) = -1100
E. 130 - ( 27 - (36 + 128).2))3
= 130 - ( 27 - 328).3
= 130 - (-301).3
= 130 - (-903)
= 1033
2x - 15 = -11 - ( -16 )
2x - 15 = -11 + 16
2x - 15 = 5
2x = 5 + 15
2x = 20
x = 20 : 1
x = 10
Vậy x = 10
7 - 2x = -37 - ( -26 )
7 - 2x = -37 + 26
7 - 2x = -11
2x = 7 - ( - 11 )
2x = 7+ 11
2x = 18
x = 18 : 2
x = 9
Vậy x = 9
| x + 7 | = 9
TH1 :
x + 7 = 9
=> x = 9 - 7
=> x = 2
TH2 :
x - 7 = -9
=> x = -9 - 7
=> x = - 9 + ( -7 )
=> x = -16
Vậy x = 2 và x = -16
Câu cuối bn tự làm nha! ^-^
2x-15=-11-(-16)
2x-15= -11+16
2x-15=5
2x=5+15
2x=20
x=20:2
x=10
a) 1. = (-75-25) + (231-131)
= -100 + 100 = 0
2. 45/9 + 9x(-1) +1
= 5- 9 +1 = -3
3. 6. (-83) + 6.(-37) + 20.6
= 6 ( 20-83-37)
= 6. (-100) = -600
4. = 26.76 - 26.38 - 76.26 +76 .38
= 38 ( 76-26)
= 38.50 = 1900
3. 3n+2 = 3n-3 + 5 = 3(n-1) + 5
3(n-1) chia hết cho n-1 nên để 3n+2 chia hết cho n-1 thì 5 chia hết cho n-1
=> n-1 thuộc tập cộng trừ 1; 5
kẻ bảng => n = 2; 0; 6; -4
d) Ta có: \(32\%-0.25:x=-\dfrac{17}{5}\)
\(\Leftrightarrow0.25:x=\dfrac{8}{25}+\dfrac{17}{5}=\dfrac{93}{25}\)
hay \(x=\dfrac{25}{372}\)
Vậy: \(x=\dfrac{25}{372}\)
e) Ta có: \(\left(x+\dfrac{1}{5}\right)^2+\dfrac{17}{25}=\dfrac{26}{25}\)
\(\Leftrightarrow\left(x+\dfrac{1}{5}\right)^2=\dfrac{9}{25}\)
\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{5}=\dfrac{3}{5}\\x+\dfrac{1}{5}=-\dfrac{3}{5}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{5}\\x=-\dfrac{4}{5}\end{matrix}\right.\)
Vậy: \(x\in\left\{\dfrac{2}{5};-\dfrac{4}{5}\right\}\)
f) Ta có: \(-\dfrac{32}{27}-\left(3x-\dfrac{7}{9}\right)^3=-\dfrac{24}{27}\)
\(\Leftrightarrow\left(3x-\dfrac{7}{9}\right)^3=\dfrac{-8}{27}\)
\(\Leftrightarrow3x-\dfrac{7}{9}=-\dfrac{2}{3}\)
\(\Leftrightarrow3x=\dfrac{1}{9}\)
hay \(x=\dfrac{1}{27}\)
g) Ta có: \(60\%\cdot x+0.4x+x:3=2\)
\(\Leftrightarrow\dfrac{4}{3}x=2\)
hay \(x=\dfrac{3}{2}\)
Vậy: \(x=\dfrac{3}{2}\)
h) PT \(\Leftrightarrow\left|\dfrac{20}{9}-x\right|=\dfrac{2}{9}\) \(\Rightarrow\left[{}\begin{matrix}\dfrac{20}{9}-x=\dfrac{2}{9}\\x-\dfrac{20}{9}=\dfrac{2}{9}\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=\dfrac{22}{9}\end{matrix}\right.\)
Vậy ...
i) PT \(\Leftrightarrow\dfrac{8}{5}+\dfrac{2}{5}x=\dfrac{16}{5}\) \(\Leftrightarrow\dfrac{2}{5}x=\dfrac{8}{5}\) \(\Leftrightarrow x=4\)
Vậy ...
1. a) 37.26 + (-26).63
= 37.26 - 26.63
= 26.(37 - 63)
= 26. -26
= -676
b) (-54).(-37) + 37.49
= 54.37 + 37.49
= 37.(54 + 49)
= 37.103
= 3811
c) (-159).26 - (-26).59
= (-159).26 + 26.59
= 26.(59 - 159)
= 26.-100
=-2600
2. a) 4 - 2x = -56
=> 2x = 60
=> x = 30
b) -9x + 42 = -66
=> -9x = -108
=> x = 12
c) 5.|x - 11| = 125
=> |x - 11| = 25
=> x -11 = -25 hoặc x -11 = 25
=> x = -14 hoặc x = 36
d) (2x + 1)2 = 81
=> 2x + 1 = -9 hoặc 2x + 1 = 9
=> 2x = -10 hoặc 2x = 8
=> x = -5 hoặc x = 4
a) 26(37-63)=-676
b)37(54+49)=3811
c)26(-159+59)=-2600
2.
a)2x=4--56=60
x=30
b)-9x=-108
x=12
c)(x-11)^2=25
*x-11=25
x=36
x-11=-25
x=-14
d)(2x+1)^2=81
2x+1=9
x=4