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Bài 1
a, 32.(-64) - 64. 68
= -64.(32 + 68)
= -64 .100
= - 6400
b, -54.76 + 12.(-76) - 76.34
= -76.(54 + 12 + 34)
= -76.100
= -7600
19- 42.(-19) + 38.5
= 19 + 42.19 + 19.2.5
= 19.(1 + 42 + 10)
= 19.53
= 1007
a) 42 - x = 5
x = 42 - 5
x = 37
b) 15.(x + 4) = 75
x + 4 = 75 : 15
x + 4 = 5
x = 5 - 4
x = 1
d) x + 18 = 12
x = 12 - 18
x = -6
e) 2x - 15 = -19
2x = (-19) + 15
2x = -4
x = -4 : 2
x = -2
f) 36 : (x^3 - 12) = -3
x^3 - 12 = 36 : (-3)
x^3 - 12 = -12
x^3 = 0
=> x = 0
g)x + 15 = 35
x = 35 - 15
x = 20
h) 2x - 13 = 3^2
2x - 13 = 9
2x = 9 + 13
2x = 22
x = 22 : 2
x = 11
a: \(=-57\cdot75+57\cdot36-75\cdot36+75\cdot57\)
\(=36\left(57-75\right)=-18\cdot36=-648\)
b: \(=19+19\cdot42+19\cdot10\)
\(=19\cdot62=1178\)
a) \(5\left(x-7\right)=0\)
\(\Rightarrow x-7=0\)
\(\Rightarrow x=7\)
b) \(25\left(x-4\right)=0\)
\(\Rightarrow x-4=0\)
\(\Rightarrow x=4\)
c) \(\left(34-2x\right)\left(2x-6\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}34-2x=0\\2x-6=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}2x=34\\2x=6\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=17\\x=3\end{matrix}\right.\)
d) \(\left(2019-x\right)\left(3x-12\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}2019-x=0\\3x-12=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=2019\\3x=12\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=2019\\x=\dfrac{12}{3}=4\end{matrix}\right.\)
e) \(57\left(9x-27\right)=0\)
\(\Rightarrow9x-27=0\)
\(\Rightarrow9\left(x-3\right)=0\)
\(\Rightarrow x-3=0\)
\(\Rightarrow x=3\)
a) 5.(x-7)=0⇔x-7=0⇔x=7
b) 25(x-4)=0⇔x-4=0⇔x=4
c) (34-2x).(2x-6)=0
⇔ 34-2x=0 hoặc 2x-6=0
⇔2x=34 hoặc 2x=6
⇔ x=17 hoặc x=3
d) (2019-x).(3x-12)=0
⇔ 2019-x=0 hoặc 3x-12=0
⇔ x=2019 hoặc x=4
e) 57.(9x-27)=0
⇔ 9x-27=0
⇔ x=3
f) 25+(15-x)=30
⇔ 15-x=5
⇔ x=10
g) 43-(24-x)=20
⇔ 24-x=23
⇔ x=1
h) 2.(x-5)-17=25
⇔ 2(x-5)=42
⇔x-5=21
⇔ x=26
i) 3(x+7)-15=27
⇔ 3(x+7)=42
⇔ x+7=14
⇔ x=7
j) 15+4(x-2)=95
⇔ 4(x-2)=80
⇔ x-2=20
⇔ x=22
k) 20-(x+14)=5
⇔ x+14=15
⇔ x=1
l) 14+3(5-x)=27
⇔ 3(5-x)=13
⇔ 5-x=13/3
⇔ x=5-13/3
⇔ x=2/3
a) (x.7 + 8) : 5 = 10
x.7 + 8 = 10.5
x.7 + 8 = 50
x.7 = 50 - 8
x.7 = 42
x = 42 : 7
x = 6
b) (x + 5).19 : 13 = 57
(x + 5).19 = 57 . 13
(x + 5).19 = 741
x + 5 = 741 : 19
x + 5 = 39
x = 39 - 5
x = 34
c) 4.(36 - 4.x) = 64
36 - 4x = 64 : 4
36 - 4x = 16
4x = 36 - 16
4x = 20
x = 20 : 4
x = 5
d) 7,6 : 19 . x = 3,2
0,4 . x = 3,2
x = 3,2 : 0,4
x = 8
e) (x : 2 + 50) : 5 = 12
x : 2 + 50 = 12 . 5
x : 2 + 50 = 60
x : 2 = 60 - 50
x : 2 = 10
x = 10 . 2
x = 20
g) 280 : (17 + 3.x) = 4
17 + 3x = 280 : 4
17 + 3x = 70
3x = 70 - 17
3x = 53
x = 53/3
h) 6.(28 - 8.x) = 72
28 - 8x = 72 : 6
28 - 8x = 12
8x = 28 - 12
8x = 16
x = 16 : 8
x = 2
i) (x - 15) : 3 : 12 = 6
(x - 15) : 3 = 6 . 12
(x - 15) : 3 = 72
x - 15 = 72 . 3
x - 15 = 216
x = 216 + 15
x = 231
(3x+4):12+17=19
=>3x+4:12=19-17
=>(3x+4):12=2
=>3x+4=2x12
=>3x+4=24
=>3x=24-4
=>3x=20
=>x=20/3
tíc mình nha
Bài 1:Tính
a, \(-57\left(75-36\right)-75\left(36-57\right)-57\left(75-36\right)-75\left(36-57\right)\)
\(=-114\left(75-36\right)-150\left(36-57\right)\)
\(=-144.39-150.\left(-21\right)\)
\(=-5616+3150=-2466\)
b, \(19-42\left(-19\right)+38.5\)
\(=19+42.19+19.2.5\)
\(=19.\left(1+42+10\right)=19.53=1007\)
Chúc bạn học tốt!!!
Bài 2: Tìm x
a, \(7x\left(x-10\right)=0\)
\(\Rightarrow x\left(x-10\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x-10=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=10\end{matrix}\right.\)
b, \(\left(4-x\right)\left(2x+6\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}4-x=0\\2x+6=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=4\\x=-3\end{matrix}\right.\)
c, \(-12\left(x-5\right)+7\left(3-x\right)=5\)
\(\Rightarrow-12x+60+21-7x=5\)
\(\Rightarrow-19x=5-60-21\)
\(\Rightarrow-19x=-76\Rightarrow x=4\)
Chúc bạn học tốt!!!