D=5/6.37+1/6.43+6/7.43+10/7.59 ;E=8/9.37+2/9.47+3/10.47+9/10.59 .tính D/E
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18 tháng 9 2025
\(b.\left(1+\frac12\right)\left(1+\frac13\right)\left(1+\frac14\right)\ldots\left(1+\frac{1}{2023}\right)\)
\(=\frac32\cdot\frac43\cdot\frac54\cdot\ldots\cdot\frac{2024}{2023}\)
\(=\frac{3\cdot4\cdot5\cdot\ldots\cdot2024}{2\cdot3\cdot4\cdot\ldots\cdot2023}\)
\(=\frac{2024}{2}=1012\)
18 tháng 9 2025
\(c.D=\frac{5}{6\cdot37}+\frac{1}{6\cdot43}+\frac{6}{7\cdot43}+\frac{10}{7\cdot59}\)
\(D=7\cdot\left(\frac{5}{37\cdot42}+\frac{1}{42\cdot43}+\frac{6}{43\cdot49}+\frac{10}{49\cdot59}\right)\)
\(D=7\cdot\left(\frac{1}{37}-\frac{1}{42}+\frac{1}{42}-\frac{1}{43}+\frac{1}{43}-\frac{1}{49}+\frac{1}{49}-\frac{1}{59}\right)\)
\(D=7\cdot\left(\frac{1}{37}-\frac{1}{59}\right)\)
\(D=7\cdot\frac{22}{2183}\)
\(D=\frac{154}{2183}\)
PP
1
KS
3
9 tháng 3 2018
1/7 . 7/3 + 5/2 . 3/7 . 59/6 . 1/7
= 1/7 . (7/3 + 5/3 . 3/7 . 59/6)
= 1/7 . 131/14
= 131/98
NN
2
MH
6 tháng 2 2022
\(a,-35.12-8.35\)
\(=\left(-35\right)\left(12+8\right)\)
\(=-700\)
\(b,-23.7-7.59-18.7\)
\(=7\left(-23-59-18\right)\)
\(7.\left(-100\right)=-700\)
\(b,115-\left(-12+29\right)\)
\(=115+12-29\)
\(=98\)
\(c,3.\left(-7\right)^2+5.\left(-4\right)^3\)
\(=3.49-5.64\)
\(=147-320\)
\(=-173\)
TD
6 tháng 2 2022
a)-35.12-8-35=-35(12+8)=-35.20=-700
b)23.(-7)-7.5+(-18).7=-7(23+59+18)=-7.100=-700
c)115-(-12+29)=115+12-29=98
d)\(3\left(-7\right)^2+5\left(-4\right)^3=3.7^2-5.4^3=3.49-5.64=147-320-173\)
Ta có; \(D=\frac{5}{6\cdot37}+\frac{1}{6\cdot43}+\frac{6}{7\cdot43}+\frac{10}{7\cdot59}\)
\(=7\left(\frac{5}{37\cdot42}+\frac{1}{42\cdot43}+\frac{6}{43\cdot49}+\frac{10}{49\cdot59}\right)\)
\(=7\left(\frac{1}{37}-\frac{1}{42}+\frac{1}{42}-\frac{1}{43}+\frac{1}{43}-\frac{1}{49}+\frac{1}{49}-\frac{1}{59}\right)\)
\(=7\left(\frac{1}{37}-\frac{1}{59}\right)\)
Ta có: \(E=\frac{8}{9\cdot37}+\frac{2}{9\cdot47}+\frac{3}{10\cdot47}+\frac{9}{10\cdot59}\)
\(=5\left(\frac{8}{37\cdot45}+\frac{2}{45\cdot47}+\frac{3}{47\cdot50}+\frac{9}{50\cdot59}\right)\)
\(=5\left(\frac{1}{37}-\frac{1}{45}+\frac{1}{45}-\frac{1}{47}+\frac{1}{47}-\frac{1}{50}+\frac{1}{50}-\frac{1}{59}\right)\)
\(=5\left(\frac{1}{37}-\frac{1}{59}\right)\)
Do đó: \(\frac{D}{E}=\frac75\)