` a) ` ` 99^20 = (99^2)^10 = 9801^10 `
Vì: `9801^10 < 9999^10 (9801 < 9999) `
` => 99^20 < 9999^10 `
` b) ` ` (27^5)^5=14348907^5 `
` (32^3)^5=32768^5 `
Vì ` 14348907^5>32768^5(14348907>32768) `
` ⇒27^25>32^15 `
` c) ` ` 2^84 và 5^35 `
` (2^12)^7=4096^7 `
` (5^5)^7=3125^7 `
Vì `4096^7>3125^7(4096>3125)`
`⇒2^84>5^35`