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=> 5(16 + x) = 245 - 140 = 105
=> 16 + x = 105 : 5 = 21
=> x = 21 - 16 = 5
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(1225 + 625) - 4x = 1000 - 150
=> 1850 - 4x = 950
=> 4x = 1850 - 950
=> 4x = 900
=> x = 900 : 4
=> x = 225
b) 43 - (24 - x) = 20
=> 24 - x = 43 - 20
=> 24 - x = 23
=> x = 24 - 23
=> x = 1
c) 245 - 5(16 + x) = 140
=> 5(16 + x) = 245 - 140
=> 5(16 + x) = 105
=> 16 + x = 105 : 5
=> 16 + x = 21
=> x = 21 - 16
=> x = 5
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a, 245 - 5 . ( 16 + x ) = 140
5 . ( 16 + x ) = 245 - 140
5 . ( 16 + x ) = 145
16 + x = 145 : 5
16 + x = 29
x = 29 - 16
x = 13 .
b, ( x - 1945 ) . 5 = 50
x - 1945 = 50 : 5
x - 1945 = 10
x = 10 + 1945
x = 1955 .
c, 30 . ( 60 - x ) = 30
60 - x = 30 : 30
60 - x = 1
x = 60 - 1
x = 59 .
d, [ ( 250 - 25 ) : 15 ] : x = ( 450 - 60 ) : 130
[ 225 : 15 ] : x = 390 : 130
15 : x = 3
x = 15 : 3
x = 5 .
e, x : [ ( 1800 + 600 ) ] = 560 : ( 315 - 35 )
x : 2400 = 560 : 280
x : 2400 = 2
x = 2 . 2400
x = 4800 .
f, x . ( x + 1 ) = 2 + 4 + 6 + 8 + 10 + ... + 2500
2 + 4 + 6 + 8 + 10 + ... + 2500
Số số hạng của dãy số trên là :
( 2500 - 2 ) : 2 + 1 = 1250 ( số hạng )
=> 2 + 4 + 6 + 8 + 10 + 2500
= ( 2 + 2500 ) . 1250 : 2
= 2502 . 1250 : 2
= 3127500 : 2
= 1563750 .
Ta có :
x . ( x + 1 ) = 1563750
Mà : 1563750 = 1250 . 1251
=> x = 1250 .
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4) 245 - 5 ( 16 + x ) = 140
5 ( 16 + x ) = 245 - 140
5 ( 16 + x ) = 105
( 16 + x ) = 105 : 5
16 + x = 21
x = 21 - 16
x = 5
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2^{x+5}+16=2^x+140\)
=> \(2^x.2^5-2^x=140-16\)
=> \(2^x\left(32-1\right)=124\)
=> \(2^x=124:31 =4=2^2\)
=> \(x=2\)
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a) b)
(x-140):7=3 720:[41-(2x+5)]=10
x-140=21 41-(2x+5)=72
x=161 2x+5=(-31)
2x=(-36)
x=-18
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a)\(280-\left(x-140\right):35=270\)
\(\Leftrightarrow\left(x-140\right):35=10\)
\(\Leftrightarrow x-140=350\)
\(\Leftrightarrow x=490\)
b) \(\left(190-2x\right):35-32=16\)
\(\Leftrightarrow\left(190-2x\right):35=48\)
\(\Leftrightarrow190-2x=1680\)
\(\Leftrightarrow2x=-1490\Leftrightarrow x=-745\)
c) \(720:\left[41-\left(2x-5\right)\right]=2^3.5\)
\(\Leftrightarrow720:\left[41-\left(2x-5\right)\right]=40\)
\(\Leftrightarrow41-\left(2x-5\right)=18\)
\(\Leftrightarrow2x-5=23\)
\(\Leftrightarrow2x=28\Leftrightarrow x=14\)
280-(x-140):35=270
(x-140):35=280-270
(x-140):35=10
(x-140)=10×35
(x-140)=350
x=350-140
x=210
vậy x=210
(192-2x):35-32=16
(192-2x):35=16+32
(192-2x):35=48
(192-2x)=48×35
(192-2x)=1680
2x=192-1680
2x=-1488
x=-1488:2
x=-744
vậy x=-744
=> 5(16 + x) = 245 - 140
=> 5(16 + x) = 105
=> 16 + x = 105 : 5
=> 16 + x = 21
=> x = 21 - 16
=> x = 5
245-5(16+x)=140
5(16+x)=245-140
5(16+x)=105
(16+x)=105:5
(16+x)=21
x=21-16
x=5