\(A=\frac{3}{54}+\frac{5}{126}+\frac{7}{294}+\frac{8}{609}\)

\(\Rightarrow A=\frac{3}{9.6}+\frac{5}{2.7.9}+\frac{7}{7.7.6}+\frac{8}{3.7.29}\)

\(\Rightarrow A=\frac{1}{18}+\frac{5}{7.18}+\frac{1}{6.7}+\frac{8}{3.7.29}\)

\(\Rightarrow A=\frac{7+5}{7.18}+\frac{1}{6.7}+\frac{8}{3.7.29}\)

\(\Rightarrow A=\frac{2}{7.3}+\frac{1}{6.7}+\frac{8}{3.7.29}\)

\(\Rightarrow A=\frac{1}{3.7}\left(\frac{2}{1}+\frac{1}{2}+\frac{8}{29}\right)\)

\(\Rightarrow A=\frac{1}{21}\left(\frac{116+29+16}{58}\right)\)

\(\Rightarrow A=\frac{1}{21}.\frac{161}{58}\)

\(\Rightarrow A=\frac{161}{1218}=\frac{23}{174}\)

Vậy \(A=\frac{23}{174}\)

23/174

A=3/54+5/126+7/294+8/609

=1/18+5/126+1/42+8/609

=2/21+15/406

=23/174

tick cho mik nha

\(\frac{23}{174}\)nha bạn

A=3/54+5/126+7/294+8/609

=1/18+5/126+1/42+8/609

=2/21+15/406

=23/174

tick cho mik nha

M=3/10+4/45+5/126+6

bấm máy 

ra nghiêm sau

M=\(\frac{25}{54}\)

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

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

= 1  +       1                   +         1             +        1         =  4

\(\dfrac{42x45}{5x7}=\dfrac{7x6x5x9}{5x7}=\dfrac{54}{1}=54\)

\(\dfrac{54x56}{7x9}=\dfrac{6x9x7x8}{7x9}=\dfrac{48}{1}=48\)

`(42 xx45)/(5xx7) =( 6xx7xx9xx5)/(5xx7) = 6 xx9 = 54`

`(54xx56)/(7xx9) = (9xx6xx7xx8)/(7xx9) = 6xx8 = 48`

đúng

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

a) 145 + 86 + 14 + 55 = ( 145 + 55 ) + (86 + 14 )

= 200 + 100

= 300

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

= 20 + 20 + 5

= 45