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\(\Leftrightarrow\left(\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}+...+\dfrac{1}{19}-\dfrac{1}{21}\right)-x+\dfrac{221}{231}=\dfrac{4}{3}\)
\(\Leftrightarrow\dfrac{10}{231}+\dfrac{221}{231}-x=\dfrac{4}{3}\)
=>1-x=4/3
hay x=-1/3
\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{21}\right).462-\frac{17}{x+1,05}=19.\)
\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{21}\right)462-\frac{17}{x+1,05}=19\)
\(\Leftrightarrow20-\frac{17}{x+1,05}=19\)
\(\Leftrightarrow1-\frac{17}{x+1,05}=0\)
\(\Leftrightarrow x+1,05=17\)
\(\Leftrightarrow x=15,95\)
Ta có : \(\left(\frac{2}{11.13}+\frac{2}{13.15}+...+\frac{2}{19.21}\right)642-\left[0,04:\left(x+1,05\right)\right]:0,12=19\)
=> \(\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{21}\right)642-0,04:\left(x+1,05\right):0,12=19\)
=>
(nãy bấm nhầm) tiếp nà :
=> \(\left(\frac{1}{11}-\frac{1}{21}\right)462-0,04:\left(x+1,05\right):0,12=19\)
=> \(\frac{10}{231}.462-0,04:\left(x+1,05\right):0,12=19\)
=> \(20-0,04:\left(x+1,05\right):0,12=19\)
=> 0,04 : (x + 1,05) : 0,12 = 1
=> 0,04 : (x + 1,05) = 0,12
=> \(x+1,05=\frac{1}{3}\)
=> \(x=\frac{1}{3}-1,05=...\)
a, -19 + (13 - x) = -2
13 - x = -2 - 19
13 - x = -21
=> x = 13 - (-21)
=> x = 33
b, 11 + x - 24 = 21
x - 24 = 21 - 11
x - 16 = 10
=> x = 10 + 16
=> x = 26
15 - ( 3 + 2x ) = 22
<=> 15 - ( 3 + 2x ) = 4
<=> 3 + 2x = 11
<=> 2x = 8
<=> x = 4
Vậy x = 4
-11 - ( 19 - x ) = 50
<=> 19 - x = -61
<=> x = 80
Vậy x = 80
2x * | +4 | = 6
<=> 2x * 4 = 6
<=> 2x = 3/2
<=> x = 3/4
Vậy x = 3/4
( 7 + x ) - ( 21 - 13 ) = 32
<=> 7 + x - 8 = 32
<=> x - 8 = 25
<=> x = 33
Vậy x = 33
*15 - ( 3 + 2x ) = 22
15 - ( 3 + 2x ) = 4
3 + 2x = 15 - 4
3 + 2x = 11
2x = 11 - 3
2x = 8
x = 8 : 2 = 4
* -11 - ( 19 - x ) = 50
19 - x = -11 - 50
19 - x = -61
x = 19 - ( -61 )
x = 80
* 2x . |+4| = 6
=> 2x . 4 = 6
2x = 6 : 4
2x = 3/2
x = 3/2 : 2 = 3/4
* ( 7 + x ) - ( 21 - 13 ) = 32
( 7 + x ) - 8 = 32
7 + x = 32 + 8
7 + x = 40
x = 40 - 7
x = 33
`(2/(11.13)+2/(13.15)+....+2/(19.21)).462-[0,04/(x+1,05):0,12=19`
`=>(1/11-1/13+1/13-1/15+....+1/19-1/21).462-(2/(50(x+1,05)).25/3=19`
`=>(1/11-1/21).462-1/(3(x+1,05))=19`
`=>10/231. 462-1/(3x+3,15)=19`
`=>20-1/(3x+3,15)=19
`=>1/(3x+3,15)=1`
`=>3x+3,15=1`
`=>3x=-2,15`
`=>x=-43/60`
Vậy `x=-43/60`
cần viết rõ ràng hơn