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Ta có : \(72^{45}-72^{44}=72^{44}\times\left(72-1\right)=72^{44}\times71\)
\(72^{44}-72^{43}=72^{43}\times\left(72-1\right)=72^{43}\times71\)
\(\Rightarrow72^{45}-72^{44}>72^{44}-72^{43}\)
cái này mình học ròi
\(72^{45}-72^{44}=72^{44}.72-72^{44}.1=72^{44}.\left(72-1\right)=72^{44}.71\)
\(72^{44}-72^{43}=72^{43}.72-72^{43}.1=72^{43}.\left(72-1\right)=72^{43}.71\)
vì \(72^{44}.71>72^{43}.71\)nên \(72^{45}-72^{44}>72^{44}-72^{43}\)
\(72^{45}-72^{44}=72^{44}\times\left(72-1\right)=72^{44}\times71\)
\(72^{44}-72^{43}=72^{43}\times\left(72-1\right)=72^{43}\times71\)
Vì \(44>43\Rightarrow72^{44}>72^{43}\Rightarrow72^{44}\times71>72^{43}\times71\)
\(\Rightarrow72^{45}-72^{44}>72^{44}-71^{43}\)
\(72^{45}-72^{44}=72^{44}.\left(72-1\right)=72^{44}.71\)
\(72^{44}-72^{43}=72^{43}.\left(72-1\right)=72^{43}.71\)
VÌ \(77^{44}.71>72^{43}.71\)
Nên \(72^{45}-72^{44}>72^{43}.71\)
\(72^{45}-72^{44}=72^{44}.\left(72-1\right)=72^{44}.71\)
\(72^{44}-72^{43}=72^{43}.\left(72-1\right)=72^{43}.71\)
Ta thấy: 7244.71 > 7243.71
=> \(72^{45}-72^{44}>72^{44}-72^{43}\)
a) Vì a - 5 ≥ b - 5 => a - 5 + 5 ≥ b - 5 + 5
=> a ≥ b
b) Vì 15 + a ≤ 15 + b => 15 + a -15 ≤ 15 + b -15
=> a ≤ b
Ta có:+) \(72^{45}-72^{44}=72^{44}.\left(72-1\right)\)
\(=72^{44}.71\)
+) \(72^{44}-72^{43}=72^{43}.\left(72-1\right)\)
\(=72^{43}.71\)
Vì \(72^{43}< 72^{44}\) \(\implies\) \(72^{43}.71< 72^{44}.71\)
\(\implies\) \(72^{44}-72^{43}< 72^{75}-72^{44}\)
7245-7244=72(45-44)=721=72
7244-7243=72(44-43)=721=72
\(\Rightarrow\)7245-7244=7244-7243
\(72^{45}-72^{44}=72^{44}.72-72^{43}.72=72.\left(72^{44}-72^{43}\right)\)
Vì \(72\left(72^{44}-72^{43}\right)>72^{44}-72^{43}\)
=> \(72^{45}-72^{44}>72^{44}-72^{43}\)
+Ta co : 7245-744=721=72
7244-7243=721=72
Do 72=72
Vay 7245-7244=7244-7243
\(72^{45}-72^{44}=72^{44}\left(72-1\right)=72^{44}.71\)
\(72^{44}-72^{43}=72^{43}\left(72-1\right)=72^{43}.71\)
\(Vì\) \(72^{44}.71>72^{43}.71\)
\(\Rightarrow72^{45}-72^{44}>72^{44}-72^{43}\)