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=15/17 x (4/7 + 3/7) - 1/3
=15/17 x 1 - 1/3
=15/17 x (3/3 - 1/3)
=15/17 x 2/3
=30/51
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 !
a) \(\dfrac{16}{15}+\dfrac{7}{15}+\dfrac{4}{15}=\left(\dfrac{16}{15}+\dfrac{4}{15}\right)+\dfrac{7}{15}=\dfrac{20}{15}+\dfrac{7}{15}=\dfrac{27}{15}\)
b) \(\dfrac{5}{17}+\dfrac{7}{17}+\dfrac{13}{17}=\dfrac{5}{17}+\left(\dfrac{7}{17}+\dfrac{13}{17}\right)=\dfrac{5}{17}+\dfrac{20}{17}=\dfrac{25}{17}\)
\(\frac{3}{5}\times\frac{6}{7}+\frac{3}{5}:7+\frac{6}{5}\)
\(=\frac{3}{5}\times\frac{6}{7}+\frac{3}{5}\times\frac{1}{7}+\frac{6}{5}\)
\(=\frac{3}{5}\times\left(\frac{6}{7}+\frac{1}{7}\right)+\frac{6}{5}\)
\(=\frac{3}{5}\times1+\frac{6}{5}\)
\(=\frac{3}{5}+\frac{6}{5}=\frac{9}{5}\)
~ Hok tốt ~
\(\frac{29}{12}:\frac{1}{2}-\frac{5}{12}:\frac{1}{2}-\frac{1}{2}\)
\(=\left(\frac{29}{12}-\frac{5}{12}\right):\frac{1}{2}-\frac{1}{2}\)
\(=2:\frac{1}{2}-\frac{1}{2}\)
\(=4-\frac{1}{2}=\frac{7}{2}\)
~ Hok tốt ~
a) \(\dfrac{3}{5}\times\dfrac{17}{21}+\dfrac{17}{21}\times\dfrac{2}{5}\)
\(=\dfrac{17}{21}\times\left(\dfrac{3}{5}+\dfrac{2}{5}\right)\)
\(=\dfrac{17}{21}\times1\)
\(=\dfrac{17}{21}\)
b) \(\dfrac{15}{8}:\dfrac{5}{20}-\dfrac{7}{8}:\dfrac{1}{4}\)
\(=\dfrac{15}{8}\times\dfrac{20}{5}-\dfrac{7}{8}\times4\)
\(=\dfrac{15}{8}\times4-\dfrac{7}{8}\times4\)
\(=4\times\left(\dfrac{15}{8}-\dfrac{7}{8}\right)\)
\(=4\times1\)
\(=4\)
$#Shả$
`A)=5/17xx(15/34+19/34)`
`=5/17xx1=5/17`
`B)=(13/12+7/12)+1/3`
`=5/3+1/3=2`
(2/7+5/7)+4/9=1+4/9=13/9
17/11+(7/15+5/11)=17/11+7/15+5/11=(17/11+5/11)+7/15=2+5/11=27/11
A = ( 2/7 + 5/7 ) + 4/9
A = 1 + 4/9
A = 13/9
B = ( 17/11 + 5/11 ) + 7/15
B = 2 + 7/15
B = 37/15
Chúc bạn học tốt~^^
A = 2/7 + 4/9 + 5/7
A = ( 2/7 + 5/7 ) + 4/9
A = 1 + 4/9
A = 13/9
Phần B làm tương tự bằng cách bỏ ngoặc nhé !
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20
=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+20+10
=20+20+20+20+20+20+20+20+20+20+10
=20×10+10
=200+10
=210
= ( 1 + 19 ) + ( 2 + 18 ) + ( 3 + 17 ) + (4 + 16 ) + ( 5 + 15 ) + ( 6 + 14 ) + ( 7 + 13 ) + ( 8 + 12) + ( 9+ 11 ) + 20
= 20 + 20 + 20 +20 + 20 +20 + 20 + 20 + 20 +20
= 20 x 10
= 200
tui đầu tiên đó