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19 tháng 8 2023
Each term of S is n!(n2 + n + 1) = n![n(n + 1) + 1] = n(n + 1)n! + n!
By definition, n(n + 1)n! + n! = n! + n(n + 1)!
Therefore, S can be simplified as
1! + 1.2! + 2! + 2.3! + ... + 100! + 100.101!
So \(\dfrac{S+1}{101!}=\dfrac{1+1!+1\cdot2!+2!+2\cdot3!+...+100!+100\cdot101!}{101!}\)
\(=\dfrac{2!+1\cdot2!+2!+2\cdot3!+3!+...+100!+100\cdot101!}{101!}\)
\(=\dfrac{3!+2\cdot3!+3!+...+100!+100\cdot101!}{101!}\)
\(=\dfrac{4!+3\cdot4!+4!+...+100!+100\cdot101!}{101!}\)
\(=...\)
\(=\dfrac{100!+99\cdot100!+100!+100\cdot101!}{101!}\)
\(=\dfrac{101!+100\cdot101!}{101!}\)
\(=1+100=101\)
Hence, \(\dfrac{S+1}{101!}=101\)
H9
HT.Phong (9A5)
CTVHS
22 tháng 6 2023
\(A=\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+\dfrac{1}{3^4}+...+\dfrac{1}{3^{99}}\)
\(\Rightarrow\dfrac{A}{3}=\dfrac{1}{3^2}+\dfrac{1}{3^3}+\dfrac{1}{3^4}+...+\dfrac{1}{3^{100}}\)
\(\Rightarrow A-\dfrac{A}{3}=\dfrac{2A}{3}=\left(\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{99}}\right)-\left(\dfrac{1}{3^2}+\dfrac{1}{3^3}+\dfrac{1}{3^4}+...+\dfrac{1}{3^{100}}\right)\)
\(\Rightarrow\dfrac{2A}{3}=\left(\dfrac{1}{3^2}-\dfrac{1}{3^2}\right)+\left(\dfrac{1}{3^3}-\dfrac{1}{3^3}\right)+...+\left(\dfrac{1}{3^{99}}-\dfrac{1}{3^{99}}\right)+\left(\dfrac{1}{3}-\dfrac{1}{3^{100}}\right)=\dfrac{1}{3}-\dfrac{1}{3^{100}}\)
\(\Rightarrow2A=3\cdot\left(\dfrac{1}{3}-\dfrac{1}{3^{100}}\right)\)
\(\Rightarrow\text{A}=\dfrac{1-\dfrac{1}{3^{99}}}{2}\)
\(\Rightarrow A=\dfrac{1}{2}-\dfrac{1}{2.3^{99}}< \dfrac{1}{2}\)
HC
0
NM
1
H9
HT.Phong (9A5)
CTVHS
21 tháng 9 2023
Ta có:
\(M=\dfrac{100^{100}+1}{100^{99}+1}\)
\(\Rightarrow\dfrac{M}{100}=\dfrac{100^{100}+1}{100\cdot\left(100^{99}+1\right)}\)
\(\Rightarrow\dfrac{M}{100}=\dfrac{100^{100}+1}{100^{100}+100}\)
\(\Rightarrow\dfrac{M}{100}=1-\dfrac{99}{100^{100}+100}\)
\(N=\dfrac{100^{101}+1}{100^{100}+1}\)
\(\Rightarrow\dfrac{N}{100}=\dfrac{100^{101}+1}{100\cdot\left(100^{100}+1\right)}\)
\(\Rightarrow\dfrac{N}{100}=\dfrac{100^{101}+1}{100^{101}+100}\)
\(\Rightarrow\dfrac{N}{100}=1-\dfrac{99}{100^{101}+100}\)
Mà: \(100^{101}>100^{100}\)
\(\Rightarrow100^{101}+100>100^{100}+100\)
\(\Rightarrow\dfrac{99}{100^{101}+100}< \dfrac{99}{100^{100}+100}\)
\(\Rightarrow1-\dfrac{99}{101^{101}+100}< 1-\dfrac{99}{100^{100}+100}\)
\(\Rightarrow\dfrac{N}{100}< \dfrac{M}{100}\)
\(\Rightarrow N< M\)
EC
2
20 tháng 10 2015
M= \(\frac{100^{100}+1}{100^{99}+1}=\frac{100^{100}+100-99}{100^{99}+1}=\frac{100^{100}+100}{100^{99}+1}-\frac{99}{100^{99}+1}=\frac{100.\left(100^{99}+1\right)}{100^{99}+1}-\frac{99}{100^{99}+1}\)
\(=100-\frac{99}{100^{99}+1}\)
N= \(\frac{100^{101}+1}{100^{100}+1}=\frac{100^{101}+100-99}{100^{100}+1}=\frac{100^{101}+100}{100^{100}+1}-\frac{99}{100^{100}+1}\)
\(=\frac{100.\left(100^{100}+1\right)}{100^{100}+1}-\frac{99}{100^{100}+1}=100-\frac{99}{100^{100}+1}\)
Vi 100100+1>10099+1
=> \(\frac{99}{100^{99}+1}>\frac{99}{100^{100}+1}\)
=> \(100-\frac{99}{100^{99}+1}
4 tháng 10 2023
\(M=\left(100-1\right)\left(100-2^2\right)...\left(100-50^2\right)\)
\(M=\left(100-1\right)\left(100-2^2\right)...\left(100-10^2\right)...\left(100-50^2\right)\)
\(M=\left(100-1\right)\left(100-2^2\right)...\left(100-100\right)...\left(100-50^2\right)\)
\(M=\left(100-1\right)\left(100-2^2\right)...0...\left(100-50^2\right)\)
\(M=0\)
HQ
Hà Quang Minh
Giáo viên
19 tháng 9 2023
Ta có:
\(\begin{array}{l}M = \left( {{{10}^2} - 1} \right).\left( {{{10}^2} - {2^2}} \right).\left( {{{10}^2} - {3^2}} \right).\,\,...\left( {{{10}^2} - {{10}^2}} \right)..\,\,.\left( {100 - {{50}^2}} \right)\\ = \left( {{{10}^2} - 1} \right).\left( {{{10}^2} - {2^2}} \right).\left( {{{10}^2} - {3^2}} \right).... 0 ...\left( {100 - {{50}^2}} \right)\\ = 0\end{array}\)
DH
4 tháng 11 2018
bài 2 :
I x+1 I + I x+2 I +.......+ I x+100 I =605.x
Do : I x+1 I >= x+1
I x+2 I >= x+2
....
I x+100 I = x+100
=> I x+1 I + I x+2 I +... I x+100 I = x+1 + x+2 + .... + x + 100 = 100x + ( 1+2+....+100) = 100x + 5050 = 605x
=> 605x -100x = 5050
=> 505x = 5050
=> x = 10
-> M = (100 – 1).(100 – 2^2). (100 – 3^2)…(100 – 50^2)
M = (100 – 1).(100 – 2^2). (100 – 3^2)… (100 – 9^2) .(100 – 10^2) .(100 – 11^2) …(100 – 50^2)
M = (100 – 1).(100 – 2^2). (100 – 3^2)… (100 – 9^2). (100 – 100) .(100 – 11^2) …(100 – 50^2)
M = (100 – 1).(100 – 2^2). (100 – 3^2)… (100 – 9^2) .0.(100 – 11^2) …(100 – 50^2)
M = 0
Vậy M = 0.