x- 15 = 49
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`16/27xx13/29+16/27xx14/29`
`=16/27xx(13/29+14/29)`
`=16/27xx27/29`
`=16/29`
`48/49+15/39-18/49+15/39`
`=(48/49-18/49)+(15/39+15/39)`
`=30/49+30/39`
`=880/637`
a) `123 - 27 + 27 + 13 - 123`
`= (123 - 123) + (27 - 27) + 13`
`= 0 + 0 + 13`
`= 13`
`---`
b) `175 + 25 + 13 + 15 - 175 - 25`
`= (175-175)+(25-25)+25+13`
`=0+0+25+13`
`=28`
`---`
c) \(53\times39+47\times39+53\times21+47\times21\)
\(=\text{[}\left(53+47\right)\times39]+\left[\left(53+47\right)\times21\right]\)
\(=\left(100\times39\right)+\left(100\times21\right)\)
\(=3900+2100\)
`=6000`
`---`
d) \(49\times35+49\times16-49\times61\)
`=` \(49\times\left(35+16-61\right)\)
`=` \(49\times\left(-10\right)\)
`=-490`
10) \(\frac{x+14}{86}+\frac{x+15}{85}+\frac{x+16}{84}+\frac{x+17}{83}+\frac{x+116}{4}=0\)
\(\Leftrightarrow\)\(\frac{x+14}{86}+1+\frac{x+15}{85}+1+\frac{x+16}{84}+1+\frac{x+17}{83}+1+\frac{x+116}{4}-4=0\)
\(\Leftrightarrow\)\(\frac{x+100}{86}+\frac{x+100}{85}+\frac{x+100}{84}+\frac{x+100}{83}+\frac{x+100}{4}=0\)
\(\Leftrightarrow\)\(\left(x+100\right)\left(\frac{1}{86}+\frac{1}{85}+\frac{1}{84}+\frac{1}{83}+\frac{1}{4}\right)=0\)
\(\Leftrightarrow\)\(x+100=0\) (vì 1/86 + 1/85 + 1/84 + 1/83 + 1/4 \(\ne\)0)
\(\Leftrightarrow\)\(x=-100\)
Vậy....
X + 27 - ( -15 ) = 49
X + 27 = 49 + ( -15 )
X + 27 = 34
X = 34-27
X = 7
\(7^x=49^{15}\cdot7=7^{30}\cdot7=7^{31}\\ \Rightarrow x=31\)
( X - 20 ) × 8 - 15 = 49
( X - 20 ) × 8 = 49 + 15
( X - 20 ) × 8 = 64
X - 20 = 64 : 8
X - 20 = 8
X = 8 + 20
X = 28
Vậy X = 28
a) x + 1 5 = − 4 9
x = − 4 9 − 1 5 x = − 29 45
b) 5 7 − x = − 9 21
x = 5 7 + 9 21 x = 8 7
\(x-\left(-15+2x\right)=-49\)
\(x+15-2x=-49\)
\(x-2x=-49-15\)
\(-x=-64\)
\(x=64\)
\(x-\left(-15+2x\right)=-49\)
\(x+15-2x=-49\)
\(x-2x=-49-15\)
\(-x=-64\)
\(x=64\)
\(=\dfrac{32}{21}\cdot\dfrac{22}{16}\cdot\dfrac{49}{45}\cdot\dfrac{5}{11}\)
\(=\dfrac{32}{16}\cdot\dfrac{22}{21}\cdot\dfrac{5}{11}\cdot\dfrac{49}{45}\)
\(=2\cdot\dfrac{49}{45}\cdot\dfrac{22}{11}\cdot\dfrac{5}{21}\)
\(=4\cdot\dfrac{49}{21}\cdot\dfrac{5}{45}=4\cdot\dfrac{1}{9}\cdot\dfrac{7}{3}=\dfrac{28}{27}\)
`x-15=49`
`x=49+15`
`x=64`
x= 49 + 5
x= 64