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Tính A = \(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{49}+\frac{1}{50}}{\frac{1}{49}+\frac{2}{48}+\frac{3}{47}+...+\frac{48}{2}+\frac{49}{1}}\)
A = \(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{49}+\frac{1}{50}}{\frac{1}{49}+\frac{2}{48}+\frac{3}{47}+...+\frac{48}{2}+\frac{49}{1}}=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{49}+\frac{1}{50}}{\left(\frac{1}{49}+1\right)+\left(\frac{2}{48}+1\right)+\left(\frac{3}{47}+1\right)+...+\left(\frac{48}{2}+1\right)+\frac{50}{50}}\)
A = \(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{49}+\frac{1}{50}}{\frac{50}{49}+\frac{50}{48}+\frac{50}{47}+...+\frac{50}{2}+\frac{50}{50}}=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{49}+\frac{1}{50}}{\left(\frac{1}{49}+\frac{1}{48}+\frac{50}{47}+...+\frac{1}{2}+\frac{1}{50}\right).50}=\frac{1}{50}\)
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\(A=\frac{T}{M}\)
\(M=\frac{1}{49}+1+\frac{2}{48}+1+\frac{3}{47}+1+.........+\frac{48}{2}+1+1\)
\(=\frac{50}{49}+\frac{50}{48}+\frac{50}{47}+.........+\frac{50}{2}+1\)
\(=50.\left(\frac{1}{49}+\frac{1}{48}+\frac{1}{47}+......+\frac{1}{2}+\frac{1}{50}\right)=50.T\)
\(A=\frac{T}{50T}=\frac{1}{50}\)
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15 tháng 10 2015 lúc 10:32
tính : S = \(\frac{1}{2}+\frac{2}{3}+\frac{3}{4}+.....+\frac{48}{49}+\frac{49}{50}\)
Tính nhanh :
a) 50 . 301
b) 32 . 48 + 52 . 32 + 68 .100
a) 50 . 301
= 50 .(300 + 1)
= 50 . 300 + 50
= 50 . 3 . 100 + 50
= 150 . 100 + 50
= 15000 + 50
= 15050
b) 32 . 48 + 52 . 32 + 68 . 100
= 32 . (48 + 52) + 68 . 100
= 32 . 100 + 68 . 100
= 100 . (32 + 68)
= 100 . 100
= 10 000
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Cho S = \(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{48}+\frac{1}{49}+\frac{1}{50}\)và P = \(\frac{1}{49}+\frac{2}{48}+\frac{3}{47}+...+\frac{48}{2}+\frac{49}{1}\). Tính \(\frac{S}{P}\)
p=\(\frac{1}{49}+\frac{2}{48}+\frac{3}{47}+...+\frac{48}{2}+49\)
=\(\left(\frac{1}{49}+1\right)+\left(\frac{2}{48}+1\right)+\left(1+\frac{3}{47}\right)+...+\left(1+\frac{48}{2}\right)+\frac{50}{50}\)
=\(\frac{50}{50}+\frac{50}{49}+\frac{50}{48}+...+\frac{50}{2}\)
=\(50\left(\frac{1}{50}+\frac{1}{49}+\frac{1}{48}+...+\frac{1}{2}\right)\)
p=50*S
\(\frac{S}{\text{p}}=\frac{1}{50}\)
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e, \(\frac{49}{1}+\frac{48}{2}+\frac{47}{3}+.......+\frac{2}{48}+\frac{1}{49}=50.\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+.......+\frac{1}{50}\right)\)
\(\frac{49}{1}+\frac{48}{2}+\frac{47}{3}+...+\frac{2}{48}+\frac{1}{49}\)
\(=1+1+...+1+\frac{48}{2}+\frac{47}{3}+...+\frac{2}{48}+\frac{1}{49}\)(có 49 số 1)
\(=\left(1+\frac{48}{2}\right)+\left(1+\frac{47}{3}\right)+...+\left(1+\frac{2}{48}\right)+\left(1+\frac{1}{49}\right)+1\)
\(=\frac{50}{2}+\frac{50}{3}+...+\frac{50}{48}+\frac{50}{49}+\frac{50}{50}\)
\(=50\left(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{49}+\frac{1}{50}\right)\)
Chúc bạn học tốt.
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B1: Tính
a) (1/4)44. (1/2)12
b) \(\frac{3^{17}.81^{11}}{27^{10}.9^{15}}
\)
c)\(\frac{14^{16}.21^{32}.35^{48}}{10^{16}.15^{32}.7^{96}}\)
d)\(\frac{\left(5^4-5^3\right)^3}{125^4}\)
e)\(\frac{10^3+5.10^2+5^3}{6^3+3.6^2+3^3}\)
Tính nhanh: a) 2 + 4 + 6 + .....+ 48 + 50 b) 4 + 7 + 10 + .... + 100
a tổng các số hạng là : (50-2):2+2=26
tổng bằng :50.26:2=650
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b tổng các số hạng là : (100-4):3+4=36
tổng bằng : (4+100).36:2=1872
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tính
\(a,\left(\frac{51}{56}+\frac{8}{21}+\frac{16}{48}\right).\frac{32}{65}\)
\(b,\left(\frac{31}{20}-\frac{26}{45}\right).\frac{36}{49}\)
\(c,\frac{5}{39}.\left(7\frac{4}{5}.1\frac{2}{3}+8\frac{1}{3}.7\frac{4}{5}\right)\)
tính
a ) 64 - 4 x 6 - 48
b ) 96 - 32 : 4 - 49
a) 64 - 4 x 6 - 48
= 4 x 16 - 4 x 6 - 48
= 4 x (16 - 6) - 48
= 4 x 10 - 48
= 40 - 48
= -8
b) 96 - 32 : 4 - 49
= 96 - 8 - 49
= 39
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Tính
a )
64 - 4 x 6 - 48
= 64 - 24 - 48
= 40 - 48
= -8
b )
96 - 32 : 4 - 49
= 96 - 8 - 49
= 88- 49
=39
tk mk nha
mơn nhiều ạ
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a) 64-4x6-48
=4x16-4x6-48
=4x(16-6) - 48
=4 x 10 - 48
=40-48
=8
b)96-32:4-49
=96-8-49
=39
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