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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
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
\(a,\left(x-15\right)\times100=0\)
\(x-15=0\)
\(x=0+15\)
\(x=15\)
\(b,64\times\left(x-10\right)=128\)
\(x-10=128\div64\)
\(x-10=2\)
\(x=2+10\)
\(x=12\)
\(c,x-105\div21=15\)
\(x-5=15\)
\(x=15+5\)
\(x=20\)
\(d,\left(x-105\right)\div21=15\)
\(x-105=15\times21\)
\(x-105=315\)
\(x=315+105\)
\(x=420\)
\(d,315+\left(125-x\right)=435\)
\(125-x=435-315\)
\(125-x=120\)
\(x=125-120\)
\(x=5\)
Học tốt
1.Tính nhanh nếu có thể:
a) 22 + 23 + 89 + 77
= ( 77 + 23 ) + 22 + 89
= 100 + 22 + 89
= 122 + 89
= 211
b) 35 . 15 + 15 . 65
= 15 . ( 35 + 65 )
= 15 . 100
= 1500
c) 7^2 - 36 : 3^2
= 7^2 - 36 : 9
= 7^2 - 4
= 49 - 4
= 45
d) 476 - {5 . [409 - (8 . 3 - 21)2] - 1724}
= 476 - {5 . [409 - (24 - 21)^2] - 1724}
= 476 - {5 . [409 - (3^2)] - 1724}
= 476 - {5 . [409 - 9 ] - 1724}
= 476 - {5. 400 - 1724}
= 476 - {2000 - 1724}
= 476 - 276
= 200
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
câu d mk làm sai rồi
d) (x-15)-75=0
x-15=0+75=75
x=75+15=90
a) 35-15+x=70
=> 20+x=70
=> x=50
b) 568-(2x+14)=15
=> 2x+14=553
=> 2x=539
=> x=269,5
c) x-105:21=15
=> x-5=15
=> x=20
d) (x-105)*21=15
=> x-105=5/7
=> x=5/7+105
=> x=740/7
a, 35 - 15 + x = 70 b, 568 - (2.x + 14 )= 15
x = 70 - 35 + 15 2.x + 14 = 568 - 15
x = 50 2.x + 14 =553 => 2.x =553-14=539 =>x=539 : 2 =269.5
c, x - 105 : 21 =15 d, (x - 105) . 21 = 15
x - 105 = 15 x 21 x - 105 = 15 : 21
x - 105 = 315 x - 105 = \(\frac{5}{7}\)
x = 315+105 x = \(\frac{5}{7}\)+ 105
x = 420 x = \(\frac{740}{7}\)
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