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a,=3/13.17/29.29/34
=3/13.1/2
=3/26
b,=(4/21+25/42).19/33
=11/14.19/33
=19/42
`a, = 3/13 xx (17/29 xx 29/34)`
`= 3/13 xx 1/2`
`= 3/26`.
`b, = 19/33(4/21 + 25/42)`
`= 19/33 xx ( 33/42 )`
`= 19/42`
Lời giải:
$1+2+3+....+25$
$=(1+25)+(2+24)+(3+23)+(4+22)+(5+21)+(6+20)+(7+19)+(8+18)+(9+17)+(10+16)+(11+15)+(12+14)+13$
$=\underbrace{26+26+26+...+26}_{12}+13$
$=26\times 12+13=325$
$#Shả$
`A)=5/17xx(15/34+19/34)`
`=5/17xx1=5/17`
`B)=(13/12+7/12)+1/3`
`=5/3+1/3=2`
\(\frac{15}{34}-\frac{5}{17}+\frac{19}{34}-\frac{12}{17}\)
\(=\left(\frac{15}{34}+\frac{19}{34}\right)-\left(\frac{5}{17}+\frac{12}{17}\right)\)
\(=1-1=0\)
\(\frac{15}{34}-\frac{5}{17}+\frac{19}{34}-\frac{12}{17}\)
\(=\left(\frac{15}{34}+\frac{19}{34}\right)-\left(\frac{5}{17}+\frac{12}{17}\right)\)
\(=\frac{34}{34}-\frac{17}{17}\)
\(=1-1\)
\(=0\)
313×1729)×2934(313×1729)×2934
=313×1729×2934=313×1729×2934
=3×17×2913×29×34=3×17×2913×29×34
=3×17×2913×29×2×17=3×17×2913×29×2×17
=313×2=313×2
=326=326
421×1933+2542×1933421×1933+2542×1933
=1933×(421+2542)=1933×(421+2542)
=1933×(842+2542)=1933×(842+2542)
=1933×3342=1933×3342
=19×3333×42=19×3333×42
=1942
36 x 7 + 12 x 29
= 252 + 338
= 600
HT
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a: \(=\dfrac{21}{11}+\dfrac{12}{11}+\left(-\dfrac{9}{19}-\dfrac{3}{19}-\dfrac{6}{19}\right)=3-\dfrac{18}{19}=\dfrac{39}{19}\)
b: \(=\dfrac{2}{3}+\dfrac{4}{3}+\dfrac{3}{4}+\dfrac{7}{4}+\dfrac{4}{5}+\dfrac{16}{5}=2+4+\dfrac{5}{2}=6+\dfrac{5}{2}=\dfrac{17}{2}\)
a) 15 / 17 x 4 / 7 + 15 / 17 x 3 / 7
= 15 / 17 x (4 / 7 + 3 / 7)
=15 / 17 x 1=15 / 17
b) 29 / 12 : 1 / 2 - 5 / 12 :1 / 2
=29 / 12 x2 - 5 / 12 x 2
=(29 / 12 - 5 / 12)x2
=2x2=4
a) 15 / 17 x 4 / 7 + 15 / 17 x 3 / 7
= 15 / 17 x (4 / 7 + 3 / 7)
=15 / 17 x 1=15 / 17
b) 29 / 12 : 1 / 2 - 5 / 12 :1 / 2
=29 / 12 x2 - 5 / 12 x 2
=(29 / 12 - 5 / 12)x2
=2x2=4
chúc bạn học tốt !
\(7+12+19+24+29+34\)
\(=\left(7+24\right)+\left(12+19\right)+\left(29+34\right)\)
\(=31+31+63\)
\(=62+63=125\)
\(7+12+19+24+29+34\)
\(=\left(7+19\right)+\left(12+29\right)+\left(24+34\right)\)
\(=26+41+58\)
\(=67+58\)
\(=125\)