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Bài 1 . Tìm x biết :
a) 110,25 - x = 17,2 . 3 + 5,6
110,25 - x = 51,6 + 5,6
110,25 - x = 57,2
x = 110,25 - 57,2
x = 53,05
Vậy x = 53,05
b) 42 - x = 105 : 15 + 18
42 - x = 7 + 18
42 - x = 25
x = 42 - 25
x = 17
Vậy x = 17
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
1) (x-17)*17=0
x-17=0
x=17
2) 32(x-11)=32
x-11=1
x=12
3) (x-25)-75=0
x-25=75
x=3
4) 575-(6*x+70)=445
6*x+70=130
6*x=60
x=10
5) 315+(125-x)=435
125-x=120
x=5
6) x-105:21=15
x-5=15
x=20
7) (x-105):21=15
x-105=315
x=420
8) (x-38):19=12
x-38=228
x=266
9) (x-15)*(x-19)=0
=>x-15=0 hoặc x-19=0
x=15 hoặc x=19
10) 96-3(x+1)=42
3(x+1)=54
x+1=18
x=17
a) ( x - 17 ) . 17 = 0
=> x - 17 = 0 : 17
=> x - 17 = 0
=> x = 0 + 17
=> x = 17
b) 32 . ( x - 11 ) = 32
=> x - 11 = 32 : 32
=> x - 11 = 1
=> x = 1 + 11
=> x = 12
c) ( x - 25 ) - 75 = 0
=> x - 25 = 0 + 75
=> x - 25 = 75
=> x = 75 + 25
=> x = 100
d) 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
e) 315 + ( 125 - x ) = 435
=> 125 - x = 435 - 315
=> 125 - x = 120
=> x = 125 - 120
=> x = 5
f) x - 105 : 21 = 15
=> x - 5 = 15
=> x = 15 + 5
=> x = 20
g) ( x - 105 ) : 21 = 15
=> x -105 = 15 . 21
=> x - 105 = 315
=> x = 315 + 105
=> x = 420
h) ( x - 38 ) : 19 = 12
=> x - 38 = 12 . 19
=> x - 38 = 228
=> x = 228 + 38
=> x = 266
i) ( x - 15 ) . ( x - 19 ) = 0
=> x - 15 = 0 => x = 0 + 15 => x = 15
x - 19 = 0 => x = 0 + 19 = x = 19
=> x = 15 ; 19
j) 96 - 3( x + 1 ) = 42
=> 3( x + 1 ) = 96 - 42
=> 3( x + 1 ) = 54
=> x + 1 = 54 : 3
=> x + 1 = 18
=> x = 18 - 1
=> x = 17
42 - x = 105 : 15 + 18
42 - x = 7 + 18 = 25
x = 42 - 25 = 17
( x - 22 x 10 ) : 11 = 39
x - 220 = 39 x 11 = 429
x = 429 + 220 = 649
42 - x = 7 + 18
<=> 42 - x = 25
<=> x= 17
( x - 220) : 11 = 39
x - 220 = 429
x = 209
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) \(315+\left(125-x\right)=435\)
\(\Leftrightarrow125-x=435-315\)
\(\Leftrightarrow125-x=120\)
\(\Leftrightarrow x=125-120\)
\(\Leftrightarrow x=5\)
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
\(x-\dfrac{5}{15}=\dfrac{42}{105}\)
\(\Rightarrow x=\dfrac{42}{105}+\dfrac{5}{15}\)
\(\Rightarrow x=\dfrac{11}{15}\)