12/17+8/17=20/17+19/17=39/17

39/17

39/17

  12/17 + 19/17 + 8/17

=         31/17 + 8/17

=            39/17

Vậy.... [kết luận]

\(\frac{15}{34}-\frac{5}{17}+\frac{19}{34}-\frac{12}{17}\)

\(=\left(\frac{15}{34}+\frac{19}{34}\right)-\left(\frac{5}{17}+\frac{12}{17}\right)\)

\(=1-1=0\)

\(\frac{15}{34}-\frac{5}{17}+\frac{19}{34}-\frac{12}{17}\)

\(=\left(\frac{15}{34}+\frac{19}{34}\right)-\left(\frac{5}{17}+\frac{12}{17}\right)\)

\(=\frac{34}{34}-\frac{17}{17}\)

\(=1-1\)

\(=0\)

\(\frac{15}{34}-\frac{5}{17}+\frac{19}{34}-\frac{12}{17}\)

=\(\frac{15}{34}+\frac{19}{34}-\frac{5}{17}-\frac{12}{17}\)

=\(1-\frac{5}{17}-\frac{12}{17}\)

=\(1-\left(\frac{5}{17}+\frac{12}{17}\right)\)

=\(1-1\)

=\(0\)

Số số hạng là 19-11+1=9(số)

Tổng là: 10x9=90

=(11+19)+(12+18)+(13+17)+(14+16)+15

=30+30+30+30+15

=135

90

\(=\dfrac{5}{12}+\left(\dfrac{8}{17}+\dfrac{60}{17}\right)\\ =\dfrac{5}{12}+4=4\dfrac{5}{12}\)

=512+(817+6017)=512+4=4512

5/12 + 8/17 + 60/17

= 5/12 + 68/7

= 5/12 + 4/1

= 5/12 + 48/12

= 53/12

HT

10-11+12-13+14-15+16-17+18-19+20
= (10+20)+(-11-19)+(12+18)+(-13-17)+(14+16)-15
= 30-30+30-30+30-15
= 15

(20 + 10) - (11 + 19) + ( 12 + 18 ) - ( 13 + 17 ) + ( 14 + 16 ) - 15

= 30 - 30 + 30 - 30 - 15

= -15

(20+10)-(11+19)+(12+18)-(13+17)+(14+16)-15

=30-30+30-30-15+30

=15

1a) \(\frac{12}{17}+\frac{19}{17}+\frac{8}{17}\)

\(=\left(\frac{12}{17}+\frac{8}{17}\right)+\frac{19}{17}\)

\(=\frac{20}{17}+\frac{19}{17}\)

\(=\frac{39}{17}\)

b) \(\frac{2}{5}+\frac{7}{12}+\frac{13}{12}\)

\(=\frac{2}{5}+\frac{5}{3}\)

\(=\frac{31}{15}\)

2) \(\frac{25}{3}-x=\frac{5}{6}\)

                \(x=\frac{25}{3}-\frac{5}{6}\)

                \(x=\frac{45}{6}\)

ủng hộ tớ nha

dấu ''/'' là chia à bạn?

ai giúp mình với

\(\frac{17}{25}\times\frac{13}{19}+\frac{17}{25}\times\frac{6}{19}\)

\(=\frac{17}{25}\times\left(\frac{13}{19}+\frac{6}{19}\right)\)

\(=\frac{17}{25}\times\frac{19}{19}\)

\(=\frac{17}{25}\times1\)

\(=\frac{17}{25}\)

_HT_

\(\dfrac{17}{25}\left(\dfrac{13}{19}+\dfrac{6}{19}\right)\)

\(=\dfrac{17}{25}.1=\dfrac{17}{25}\)

bấm lộn nha

$#Shả$

`A)=5/17xx(15/34+19/34)`

`=5/17xx1=5/17`

`B)=(13/12+7/12)+1/3`

`=5/3+1/3=2`

a)12/17+19/17+8/17=(12/17+8/17)+19/17=20/17+19/17=39/17

b)2/5+7/12+13/12=2/5+(7/12+13/12)=2/5+5/3=31/15

~HT~

k cho mình nha

@@@@@@@@@@@@@