\((\frac{1}{2}+\frac{1}{4}+\frac{1}{6}) \)x \((\frac{36}{9}-\frac{12}{9}:\frac{1}{3}) \)

\(= (\frac{1}{2}+\frac{1}{4}+\frac{1}{6}) \) x \((\frac{36}{9}-\frac{36}{9})\)

\( = (\frac{1}{2}+\frac{1}{4}+\frac{1}{6}) \) x \(0\)

\(= 0\)

\(a,\\ =\left(\dfrac{4}{9}+\dfrac{5}{9}\right)+\left(\dfrac{1}{8}+\dfrac{7}{8}\right)=1+1=2\\ b,\\ =\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{2}{3}\right)\left(\dfrac{5}{12}+\dfrac{1}{12}\right)\\ =\dfrac{7\times2}{3\times2}+\dfrac{1\times3}{2\times3}=\dfrac{14+3}{6}=\dfrac{17}{6}\)

\(a,\dfrac{4}{9}+\dfrac{1}{8}+\dfrac{5}{9}+\dfrac{7}{8}=\left(\dfrac{4}{9}+\dfrac{5}{9}\right)+\left(\dfrac{1}{8}+\dfrac{7}{8}\right)=\dfrac{9}{9}+\dfrac{8}{8}=1+1=2\\ b,\dfrac{1}{3}+\dfrac{2}{3}+\dfrac{5}{12}+\dfrac{4}{3}+\dfrac{1}{12}=\left(\dfrac{1}{3}+\dfrac{2}{3}+\dfrac{4}{3}\right)+\left(\dfrac{5}{12}+\dfrac{1}{12}\right)=\dfrac{7}{3}+\dfrac{6}{12}=\dfrac{7}{3}+\dfrac{1}{2}=\dfrac{14}{6}+\dfrac{3}{6}=\dfrac{17}{6}\)

a: \(=\left(\dfrac{4}{9}+\dfrac{5}{9}\right)+\left(\dfrac{1}{8}+\dfrac{7}{8}\right)\\ =1+1=2\)

b: \(=\left(\dfrac{1}{3}+\dfrac{2}{3}\right)+\left(\dfrac{5}{12}+\dfrac{1}{12}\right)+\dfrac{4}{3}\\ =1+\dfrac{1}{2}+\dfrac{4}{3}=\dfrac{17}{6}\)

TL

1+2+3+4+5+6+7+8+9=45

nha bn

HT

1+2+3+...+9

=(1+9)+(2+8)+...+5

=10+10+...+5

=10.4+5

=45

HT

45

nha bn

HT

OK

+1

=2/3*(1/6+3/6)

=2/3*4/6

=8/18

=4/9

 Hình như đề sai đó bạn ơi ! Nếu nhân thì đâu ra cách tính thuận tiện nhất 

2/3+1/6*2/3+3/6

=2/3*(1/6+3/6)

=2/3*4/6

=4/9

tích mik nha

\(\left(\dfrac{2}{7}+\dfrac{5}{7}\right)+\left(\dfrac{3}{5}+\dfrac{2}{5}\right)+\left(\dfrac{3}{8}+\dfrac{4}{8}+\dfrac{1}{8}\right)+\left(\dfrac{1}{9}+\dfrac{8}{9}\right)=1+1+1+1=4\)

(2/7 + 5/7) + (3/5 + 2/5) + (3/8 + 4/8 + 1/8) + (1/9 + 8/9 )

= 1  +       1                   +         1             +        1         =  4

(9+1) + ( 2 + 8 ) + ( 3 + 7) + ( 4 + 6 ) + 5
=10 + 10 + 10 + 10 + 5 
= 10 x 4 + 5
= 40 + 5
= 45

1+2+3+4+5+6+7+8+9

= ( 1 + 9 ) +  ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5

= 10  x 4 + 5

= 45

~HT~

@Anh

1 + 2 + 3 + 4 + 5 + 6 + 7 +8 +9

=(1+9) + (2+8) + (3+7) + (4+6) + 5

=10 + 10 + 10 + 10 + 5

=45

Nhớ k đúng cho mk nha, thanks

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