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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
câu d mk làm sai rồi
d) (x-15)-75=0
x-15=0+75=75
x=75+15=90
a) \(315+\left(125-x\right)=435\)
\(\Leftrightarrow125-x=435-315\)
\(\Leftrightarrow125-x=120\)
\(\Leftrightarrow x=125-120\)
\(\Leftrightarrow x=5\)
b) \(x:41=32\)
\(\Leftrightarrow x=32\cdot41\)
\(\Leftrightarrow x=1312\)
c) \(\left(x-105\right):21=15\)
\(\Leftrightarrow x-105=15\cdot21\)
\(\Leftrightarrow x-105=315\)
\(\Leftrightarrow x=315+105\)
\(\Leftrightarrow x=420\)
d) \(x-105:21=15\)
\(\Leftrightarrow x-5=15\)
\(\Leftrightarrow x=15+5\)
\(\Leftrightarrow x=20\)
a, 315 + ( 125 - x ) = 435
( 125 - x) = 435 - 315
( 125 - x ) = 320
x = 320 - 125
x = 195
a) x - 105 : 21 = 15
x - 5 = 15
=> x = 20
b) ( x - 105 ) : 21 = 15
x - 105 = 315
=> x = 420
c) 315 + ( 125 - x ) = 435
125 - x = 120
=> x = 5
575-[6x+60]=25
[6x+60]=575-25
[6x+60]=550
suy ra:
6x+60=550 hoặc 6x+60=-550
6x =550-60 6x =-550-60
6x =490 6x =-610
vậy...
[x+32]-17.2=42
[x+32]-17 =42:2
[x+32]-17 =21
[x+32] =21+17
[x+32] =28
suy ra:
x+32=28 hoặc x+32=-28
x =28-32 x =-28-32
x =-4 x =-60
\(a,\left(x-15\right)\times100=0\)
\(x-15=0\)
\(x=0+15\)
\(x=15\)
\(b,64\times\left(x-10\right)=128\)
\(x-10=128\div64\)
\(x-10=2\)
\(x=2+10\)
\(x=12\)
\(c,x-105\div21=15\)
\(x-5=15\)
\(x=15+5\)
\(x=20\)
\(d,\left(x-105\right)\div21=15\)
\(x-105=15\times21\)
\(x-105=315\)
\(x=315+105\)
\(x=420\)
\(d,315+\left(125-x\right)=435\)
\(125-x=435-315\)
\(125-x=120\)
\(x=125-120\)
\(x=5\)
Học tốt
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
Bài 1: Tìm số tự nhiên x,biết:
a) 6.x-5=613
\(\Rightarrow6x=618\)
\(\Rightarrow x=618:6\)
\(\Rightarrow x=103\)
l) 0.(7-x)=0
e) x-105:21=15
x-5 =15
x =20
f) (x-105):21=15
x-105 =315
x =420
k) 5x-x=84
x(5-1)=84
x.4 =84
x =21
a) 6x-5=613
6x =613+5
6x =618
x =103
b) (x-47)-115=0
x-47 =115
x =162
c) 315+(146-x)=401
146-x =401-315
146-x =86
x =146-86
x =60
d) 575-(6x+70)=445
6x+70 =130
6x =60
x =10
Học tốt nha!!!
a, 100 - 7 x ( x - 5 ) = 58
7 x ( x - 5 ) = 100 - 58
7 x ( x - 5 ) = 42
( x - 5 ) = 42 : 7
x - 5 = 6
x = 6 + 5
x = 11
b, 24 + 5 * x = 49
5 * x = 49 - 24
5 * x = 25
x = 25 : 5
x = 5
c, x - 105 : 21 = 15
x - 5 = 15
x = 15 + 5
x = 20
d, ( x - 105 ) : 21 = 15
( x - 105 ) = 15 x 21
x - 105 = 315
x = 315 + 105
x = 420
a) 575-(6x+70)=455
6x+70=575-455
6x+70=120
6x=120-70
6x=50
x=50:6
x=\(\dfrac{25}{3}\) \(\notinℕ\)
Vậy không có giá trị tự nhiên x thỏa mãn đề
b) 315+(125-x)=435
125-x=435-315
125-x=120
x=125-120
x=5 (nhận)
c) 3x+28=88
3x=88-28
3x=60
x=60:3
x=20
\(a.575-\left(6\cdot x+70\right)=455\\ =>6\cdot x+70=575-455\\ =>6\cdot x+70=120\\ =>6\cdot x=120-70\\ =>6\cdot x=50\\ =>x=\dfrac{50}{6}=\dfrac{25}{3}\left(L\right)\\ b.315+\left(125-x\right)=435\\ =>125-x=435-315=125\\ =>x=125-125=0\\ c.3\cdot x+28=88\\ =>3\cdot x=88-28\\ =>3\cdot x=60\\ =>x=\dfrac{60}{3}=20\\ x-105:21=15\\ =>x-5=15\\ =>x=15+5=20\\ e.\left(x-105\right):21=15\\ =>x-105=21\cdot15\\ =>x-105=315\\ =>x=315+105\\ =>x=420\)