Question

So sánh:

a, 2\(^{21}\)và  5\(^{35}\)

b, 99\(^{20}\)và  9999\(^{10}\)

Answer 1

99²⁰=(99²)¹⁰=9801¹⁰.Do 9801 < 9999 nên 99²⁰<9999¹⁰

5³⁵=3125⁷;2²¹=8⁷. Do 3125>8 nên suy ra 2²¹<5³⁵

Answer 2

a)2²¹=(2³)⁷=8⁷

5³⁵=(5⁵)⁷=3125⁷

có 8<3125 suy ra 2²¹<3125⁷

Answer 3

Ta có:\(2^{21}=\left(2^3\right)^7=8^7\)

\(5^{35}=\left(5^5\right)^7=25^7\)

\(25^7>8^7=>2^{21}< 5^{35}\)

b,\(99^{20}=\left(99^2\right)^{10}=9801^{10}\)

=>\(9801^{10}< 9999^{10}=>99^{20}< 9999^{10}\)

Answer 4

a,Vì 5^35 > 4^35 = 2^70 >2^21 nên 5^35 > 2^21

b,Vì 9999^10 > 9801^10=99^20 nên 9999^10 >99^20

Answer 5

Ta có: 2²¹=(2³)⁷=8⁷

          5³⁵=(5⁵)⁷=3125⁷ 

^=> 8⁷<3125⁷

^=> 2²¹<5³⁵

Answer 6

a, Ta có:

\(2^{21}=\left(2^3\right)^7=8^7\)

\(5^{35}=\left(5^5\right)^7=3125^7\)

Vì 8<3125\(\Rightarrow\)\(8^7< 3125^7\)

\(\Rightarrow2^{21}< 5^{35}\)

Vậy \(2^{21}< 5^{35}\)

b, Ta có \(99^{20}=\left(99^2\right)^{10}=9801^{10}\)

Vì 9801<9999 

\(\Rightarrow\)\(9801^{10}< 9999^{10}\)

\(\Rightarrow99^2< 9999^{10}\)

Vậy\(99^{20}< 9999^{10}\)

Answer 7

a)2^21= (2^3)^7 = 8^7

5^35 =(5^5)^7 = 3125^7

Vì 3125^7> 8^7 nên 2^21<5^35

b) 99^20 và 9999^10

99^20=(99^2)^10= 198^10

Vì 198^10< 9999^10 nên 99^20< 9999^10

Answer 8

Bài làm:

a) \(2^{21}=\left(2^3\right)^7=8^7< 3125^7=\left(5^5\right)^7=5^{35}\)

\(\Rightarrow2^{21}< 5^{35}\)

b) \(99^{20}=\left(99^2\right)^{10}=9801^{10}< 9999^{10}\)

\(\Rightarrow99^{20}< 9999^{10}\)

Học tốt!!!!