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a) \(\left(x-15\right)-75=0\\ \Leftrightarrow x-15=75\\ \Leftrightarrow x=90\)
b) \(575-\left(6x+70\right)=445\\ \Leftrightarrow6x+70=130\\ \Leftrightarrow6x=60\\ \Leftrightarrow x=10\)
c) \(x-105:21=15\\ \Leftrightarrow x-5=15\\ \Leftrightarrow x=20\)
d) \(\left(x-105\right):21=15\\ \Leftrightarrow x-105=315\\ \Leftrightarrow x=420\)
a) ( x - 15 ) - 75 = 0
x -15 = 75 + 0
x - 15 = 75
x= 75 + 15
x = 90
b) 575- (6x +70) =445
6x + 70 = 575 - 545
6x + 70 = 130
6x = 130 - 70
6x = 60
x = 60 : 6
x = 10
c) x –105 : 21 =15
x –105 = 15 x 21
x -105 = 315
x = 315 + 105
x = 420
d) (x - 105) :21 = 15
x - 105 = 21
x = 105 + 21
x = 126
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Chỉ áp dụng cho những bn lớp 8-9 :D
\(a,\left(x-2\right)\left(2013-3x\right)=0\)
\(< =>2013x-3x^2-4026+6x=0\)
\(< =>-3x^2+2019x-4026=0\)
Ta có : \(\Delta=2019^2-4.\left(-3\right)\left(-4026\right)=4076361-48312=4028049\)
\(< =>\sqrt{\Delta}=2007\)
Vì delta > 0 nên pt có 2 nghiệm phân biệt
\(x_1=\frac{-2019+2007}{-6}=\frac{-12}{-6}=2\)
\(x_2=\frac{-2019-2007}{-6}=\frac{-4026}{-6}=671\)
Vậy ...
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a,(x-15)-75=0
x-15 =75
x =75+15
x =90
b,72-(6.x+5)=55
6.x+5=72-55
6.x+5=17
6.x=17-5
6.x=12
x=12:6
x=2
c,575-(6.x+70)=445
6.x+70=575-445
6.x+70=130
6.x=130-70
6.x=60
x=60:6
x=10
d,(x-34).15=0
x-34=0
x=34
e,15+(18-x)=26
18-x=26-15
18-x=11
x=18-11
x=7
g,(x-5):16=2
x-5=2.16
x-5=32
x=32+5
x=37
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(3x - 15) - 75 = 0
3x - 15 = 75
3x = 75 + 15
3x = 90
x = 90 : 3
x = 30
-------------------
3²ˣ⁻¹ = 27
3²ˣ⁻¹ = 3³
2x - 1 = 3
2x = 4
x = 2
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a) \(\left(x-2018\right)\cdot3=0\)
\(\Leftrightarrow x-2018=0\)
\(\Leftrightarrow x=2018\)
b) \(25\left(x-8\right)=0\)
\(\Leftrightarrow x-8=0\)
\(\Leftrightarrow x=8\)
c) \(25+\left(15+x\right)=75\)
\(\Leftrightarrow15+x=50\)
\(\Leftrightarrow x=35\)
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a: A={71;72;73;74}
b: B={41;43;45;47;49}
c: C={0}
d: D=R
A = ( 71,72,73,74 )
B = ( 41,43,45,47,49 )
C = ( 0)
D = ( 1,2,3,4,5,6,7,......., N )
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a)
2.(x-5) - 3.(x-4) = -51
2x - 10 - 3x + 12 = -51
2x - 3x = -51 + 10 - 12
-x = -53
=> x = 53
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a) ( x - 15 ) - 75 = 0
x - 15 = 75
x = 75 + 15
x = 90
Vậy x = 90
b) 575 - ( 6x + 70 ) = 445
6x + 70 = 575 - 445
6x + 70 = 130
6x = 60
x = 10
Vậy x = 10
c) 315 + ( 125 - x ) = 435
125 - x = 120
x = 125 - 120
x = 5
Vậy x = 5
d) x - 105 : 21 = 15
x - 5 = 15
x = 20
Vậy x = 20
e) ( x - 105 ) : 21 = 1
x - 105 = 21
x = 21 + 105
x = 126
Vậy x = 126
![](https://rs.olm.vn/images/avt/0.png?1311)
X x 13 = 39
X = 39 : 13
X = 3
( x - 15 ) - 75 = 0
x - 15 = 0 + 75
x - 15 = 75
x = 75 + 15
x = 90
6x - 39 = 201
6x = 201 + 39
6x = 240
x = 40
X x 13 = 39
X = 39 : 13
X = 3
( x - 15 ) - 75 = 0
x - 15 = 0 + 75
x - 15 = 75
x = 75 + 15
x = 90
6x - 39 = 201
6x = 201 + 39
6x = 240
x = 240 : 6
x = 40
575 - ( 6x +70 ) = 445
6x + 70 = 575 - 445
6x + 70 = 130
6x = 130 - 70
6x = 60
x = 60 : 6
x = 10
\(\left(x-15\right)-75=0\)
\(x-15=0+75\)
\(x-15=75\)
\(x=75+15\)
\(x=90\)
Học tốt
\(\left(x-15\right)-75=0\)
\(x-15=75\)
\(x=75+15\)
\(x=90\)
Vậy : x = 90