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Ta có : \(A=\frac{5}{3.9}+\frac{5}{9.15}+\frac{5}{5.21}+.....+\frac{5}{63.69}\)
\(\Rightarrow A=\frac{5}{6}\left(\frac{6}{3.9}+\frac{6}{9.15}+\frac{6}{15.21}+......+\frac{6}{63.69}\right)\)
\(\Rightarrow A=\frac{5}{6}\left(\frac{1}{3}-\frac{1}{9}+\frac{1}{9}-\frac{1}{15}+.....+\frac{1}{63}-\frac{1}{69}\right)\)
\(\Rightarrow A=\frac{5}{6}\left(\frac{1}{3}-\frac{1}{69}\right)\)
\(\Rightarrow A=\frac{5}{6}.\frac{22}{69}=\frac{55}{207}\)
=[\(\left(\frac{2}{3}.\frac{5}{7}+\frac{2}{3}.\frac{2}{7}\right).\left(\frac{-1}{3}\right)\)]
=[\(\left(\frac{2}{3}\right).\left(\frac{5}{7}+\frac{2}{7}\right).\left(\frac{-1}{3}\right)\)]
=[\(\left(\frac{2}{3}.1\right).\frac{-1}{3}\)]
=\(\frac{-1}{3}\)
(2/3.5/7 + 2/3: 7/2). -1/3
=(10/21 + 2/3x2/7 ) . -1/3
=(10/21 + 4/21) . -1/3
=-10/63 - 4/63
=-14/63
(2/3.5/7+2/3:7/2)-1/3
=(2/3.5/7+2/3x2/7)-1/3
=[2/3.(5/7+2/7)]-1/3
=[2/3x1]-1/3
=2/3-1/3
=1/3
HT
\(=\dfrac{11}{4}\cdot\left(-1\right)\cdot\dfrac{8}{33}=\dfrac{2}{3}\cdot\left(-1\right)=-\dfrac{2}{3}\)
\(\frac{-1}{3}:\frac{-5}{6}=\frac{-1}{3}\times\frac{-6}{5}=\frac{2}{5}\)
@muối
\(-23\cdot63+23\cdot21-58\cdot23\)
\(=23\left(-63+21-58\right)\)
\(=23\cdot\left(-100\right)\)
\(=-2300\)
= 37 . ( 28 + 82 ) + 63 . ( 69 + 41 )
= 37 . 100 + 63 . 110
= 3700 + 6930
= 10630
hok tốt
37.28 + 37.82 + 63.69 + 63.41
= 37.(28+82) + 63.(69+41)
= 37.110 + 63.110
= 110.(37+63)
= 110.100
= 11 000
37 . 28 + 37. 82 + 63 . 96 + 63 . 41
= 37 ( 28 + 82 ) + 63 ( 69 + 41 )
= 37 . 110 + 63 . 110
= ( 37 + 63 ) 110
= 100 . 110
= 11 000
Học tốt nhé bạn !
= 37( 28 + 82) + 63( 69 + 41 )
= 37 x 110 + 63 x 110
= ( 37 + 63 ) x 110
= 100 x 110
= 11000
Cảm ơn mọi người
= 37 . ( 28 + 82 ) + 63 . ( 69 + 41 )
= 37 . 100 + 63 . 110
= 3700 + 6930
= 10630
10630 nha
~HT~K cho mình nhé