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\(A=9\left(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+...+\dfrac{1}{98\cdot99}\right)\)
\(=9\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{98}-\dfrac{1}{99}\right)\)
\(=9\cdot\dfrac{98}{99}=\dfrac{98}{11}\)
A = 9/1.2 + 9/2.3 + 9/3.4 +...+ 9/98.99 + 9/99.100
= 9. (1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/98 - 1/99 + 1/99 - 1/100)
= 9. (1 - 1/100)
= 9 . 99/100
= 891/100
\(A=9\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{99}-\dfrac{1}{100}\right)=9\left(1-\dfrac{1}{100}\right)=\dfrac{891}{100}\)
\(\dfrac{-1}{9}.\dfrac{-3}{5}+\dfrac{5}{-6}.\dfrac{-3}{5}-\dfrac{7}{2}.\dfrac{3}{5}\)
\(=\dfrac{3}{5}.\left(\dfrac{1}{9}+\dfrac{5}{6}-\dfrac{7}{2}\right)\)
\(=\dfrac{3}{5}.\left(\dfrac{2}{18}+\dfrac{15}{18}-\dfrac{63}{18}\right)\)
\(=\dfrac{3}{5}.\left(-\dfrac{23}{9}\right)\)
\(=-\dfrac{69}{45}\)
`6/7 . 8/13 +6/7 . 9/13+3/13 . 6/7`
`=6/7 . (8/13+9/13+3/13)`
`=6/7 . 20/13`
`=120/91`
\(\dfrac{6}{7}.\dfrac{8}{13}+\dfrac{6}{7}.\dfrac{9}{13}+\dfrac{3}{13}.\dfrac{6}{7}\)
\(=\dfrac{6}{7}.\left(\dfrac{8}{13}+\dfrac{9}{13}+\dfrac{3}{13}\right)\)
\(=\dfrac{6}{7}.\left(\dfrac{8+9+3}{13}\right)\)
\(=\dfrac{6}{7}.\dfrac{20}{13}\)
\(=\dfrac{6.20}{7.13}\)
\(=\dfrac{120}{91}\)
\(A=9\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\right)\)
\(A=9\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(A=9\left(1-\frac{1}{100}\right)\)
\(A=9\times\frac{99}{100}\)
\(A=\frac{891}{100}\) hoặc =8,91
A=9/1.2+9/2.3+9/3.4+...+9/98.99+9/99.100
A=9.(1/1.2+1/2.3+1/3.4+...+1/98.99+1/99.100)
A=9.(1/1-1/2+1/2-1/3+1/3-1/4+...+1/98-1/99+1/99-1/100)
A=9.(1/1-1/100)
A=9.99/100
A=891/100
A=8+91/100 ( viết dưới dạng hỗn số )
Vậy A=8+91/100
Nkớ k cho mink đó nha !!!
A=9/1.2+ 9/2.3+ 9/3.4+ .... +9/98.99 + 9/99/100
=9(1- 1/2 + 1/2 -1/3+...+1/99 -1/100)
=9.(1- 1/100)
=9.99/100
=891/100
A=9/1.2+9/2.3+...+9/99.100
A/9=1/1.2+1/2.3+....+1/99.100
A/9=1-1/2+1/2-1/3+....+1/99-1/100
A/9=1+(-1/2+1/2)+(-1/3+1/3)+....+(-1/99+1/99)-1/100
A/9=1-1/100
A/9=99/100
A=99/100.9=891/100
Vậy A=891/100
mik ko biết đúng hay sai mn góp ý giúp mik nha
`5/9+4/9:x=1/3`
`=>4/9:x=1/3-5/9`
`=>4/9:x=3/9-5/9`
`=>4/9:x=-2/9`
`=>x=4/9:(-2/9)`
`=>x=4/9.(-9/2)`
`=>x=-4/2`
`=>x=-2`
\(A=\frac{9}{1.2}+\frac{9}{2.3}+\frac{9}{3.4}+...+\frac{9}{2019.2020}\)
\(=9\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{2019.2020}\right)\)
\(=9\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2019}-\frac{1}{2020}\right)\)
\(=9\left(1-\frac{1}{2020}\right)\)
\(=9.\frac{2019}{2020}\)
\(=\frac{18171}{2020}\)
\(A=\frac{9}{1.2}+\frac{9}{2.3}+\frac{9}{3.4}+...+\frac{9}{2019.2020}\)
\(A=9.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{2019.2020}\right)\)
\(A=9\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2019}-\frac{1}{2020}\right)\)
\(A=9\left(1-\frac{1}{2020}\right)=\frac{9.2019}{2020}=\frac{18171}{2020}\)
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