So sánh 1002 và 101*103
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Giải:
Ta gọi:
A=101/102+102/103
B=101+102/102+103
Ta có:
B=101+102/102+103
B=101/102+103+102/102+103
Vì 101/102+103<101/102
102/102+103<102/103
nên A>B
Chúc bạn học tốt!
M=101^102+1/101^103+1
M=101^102+1/101^102*101+1
M=1/101+2
M=1/102
N=101^103+1/101^104+1
N=101^103+1/101^103*101+1
N=1/101+1
N=1/102
Vậy N=M
\(N=\frac{101^{103}+1}{101^{104}+1}<\frac{101^{103}+1+100}{101^{104}+1+100}=\frac{101^{103}+101}{101^{104}+101}=\frac{101\left(101^{102}+1\right)}{101\left(101^{103}+1\right)}=\frac{101^{102}+1}{101^{103}+1}\)
=> N < M
Ta có:
\(M=\frac{101^{102}+1}{101^{103}+1}\)
\(101M=\frac{101^{103}+1+100}{101^{103}+1}=1+\frac{100}{101^{103}+1}\)
Ta lại có:
\(N=\frac{101^{103}+1}{101^{104}+1}\)
\(101N=\frac{101^{104}+1+100}{101^{104}+1}=1+\frac{100}{101^{104}+1}\)
Vì \(\frac{100}{101^{104}+1}< \frac{100}{101^{103}+1}\Rightarrow101N< 101M\Rightarrow N< M\)
Ta có: \(B=\frac{101+102+103}{102+103+104}=\frac{101}{102+103+104}+\frac{102}{102+103+104}+\frac{103}{102+103+104}\)
Ta thấy: \(\frac{101}{102}>\frac{101}{102+103+104}\)
\(\frac{102}{103}>\frac{102}{102+103+104}\)
\(\frac{103}{104}>\frac{103}{102+103+104}\)
\(\Rightarrow A=\frac{101}{102}+\frac{102}{103}+\frac{103}{104}>\frac{101}{102+103+104}+\frac{102}{102+103+104}+\frac{103}{102+103+104}=\frac{101+102+103}{102+103+104}=B\)
Vậy....
\(B=\frac{101+102+103}{102+103+104}=\frac{101}{102+103+104}+\frac{102}{102+103+104}+\frac{103}{102+103+104}\)
Ta có: \(\frac{101}{102}>\frac{101}{102+103+104}\)
\(\frac{102}{103}>\frac{102}{102+103+104}\)
\(\frac{103}{104}>\frac{103}{102+103+104}\)
\(\Rightarrow A=\frac{101}{102}+\frac{102}{103}+\frac{103}{104}>\frac{101}{102+103+104}+\frac{102}{102+103+104}+\frac{103}{102+103+104}=\frac{101+102+103}{102+103+104}=B\)Vậy....
Ta có :\(\frac{101}{102}>\frac{101}{102+103+104}\)
\(\frac{102}{103}>\frac{102}{102+103+104}\)
\(\frac{103}{104}>\frac{103}{102+103+104}\)
Do đó:\(\frac{101}{102}+\frac{102}{103}+\frac{103}{104}>\frac{101+102+103}{102+103+104}\)
Vậy A>B
Ta có : \(101M=\frac{101\left(101^{102}+1\right)}{101^{103}+1}=\frac{101^{103}+100+1}{101^{103}+1}=1+\frac{100}{101^{103}+1};\)
\(101N=\frac{101\left(101^{103}+1\right)}{101^{104}+1}=\frac{101^{104}+1+100}{101^{104}+1}=1\frac{100}{101^{104}+1}\)
Vì \(\frac{100}{101^{103}+1}>\frac{100}{101^{104}+1}\Rightarrow1+\frac{100}{101^{103}+1}>1+\frac{100}{101^{104}+1}\Rightarrow101M>101N\)
=> M > N
\(100^2=100.100\)
Mà 100 < 101 , 100 < 103
=> 100.100 < 101.103
=> 1002 < 101.103
Vậy 1002 < 101.103
Ta có: \(100^2\Leftrightarrow10000\) và \(101.103=10403\)
\(10000< 10403\Rightarrow100^2< 101.103\)
Cách làm khác:
Ta có: 1002 = 100 x 100
101 x 103 = 101 x 103
Ta thấy: 100 < 101 ; 100 < 103
Vậy 1002 < 101.103