a)  1024 9 = ( 2 10 ) 9 = 2 90 < 2 100

b)  6 . 5 29 > 5 . 5 29 = 5 30

c) 10 30 = ( 10 3 ) 10 = 1000 10 ; 2 100 = ( 2 10 ) 10 = 1024 10   n ê n   10 30 < 2 100 .

a. \(5^{127}=5.5^{126}=5.125^{72}>119^{72}\)

\(\Rightarrow5^{217}>119^{72}\)

b. \(2^{1000}=\left(2^5\right)^{200}=32^{200}\)

\(5^{400}=\left(5^2\right)^{200}=25^{200}\)

\(\Rightarrow2^{1000}>5^{400}\)

c. \(9^{12}=\left(3^2\right)^{12}=3^{24}\)

\(27^7=\left(3^3\right)^7=3^{21}\)

\(\Rightarrow9^{12}>27^7\)

d. \(125^{80}=\left(5^3\right)^{80}=5^{240}\)

\(25^{118}=\left(5^2\right)^{118}=5^{236}\)

\(\Rightarrow125^{80}>25^{118}\)

e. \(5^{40}=\left(5^4\right)^{10}=625^{10}\)

\(\Rightarrow5^{40}>620^{10}\)

f. \(27^{11}=\left(3^3\right)^{11}=3^{33}\)

\(81^8=\left(3^4\right)^8=3^{32}\)

\(\Rightarrow27^{11}>81^8\)

a) >

b) <

c) <

d) <

a)>

b)<

c)<

d)<

a) Cách 1:  2 100 = 2 10 10 = 1024 10 > 1024 9

Cách 2:  1024 9 = 2 10 9 =  2 90  <  2 100

b)  6 . 5 29  >  5 . 5 29  =  5 30

c)  2 98 =  2 2 49 =  4 49  <  9 49

d)  10 30 =  10 3 10 = 1000 10 ;  2 100 =  2 10 10  = 1024 10 nên  10 30  <  2 100

a) 10³⁰ và 2¹⁰⁰ .

10³⁰ = ( 10³ )¹⁰ = 1000¹⁰ .

2¹⁰⁰ = ( 210 )¹⁰ = 1024¹⁰ .

Vì 1000¹⁰ < 1024¹⁰ .

\(\Rightarrow\) 10³⁰ < 2¹⁰⁰ .

Vậy ....

b) \(\uparrow\) Lm như trên .

a, Ta có  10 30 = 10 3 10 = 1000 10

2 100 = 2 10 10 = 1024 10

Vì 1000<1024 nên  1000 10 <  1024 10

Vậy  10 30 <  2 100

b, Ta có:  333 444 = 333 4 111 = 3 . 111 4 111 =  81 . 111 4 111

444 333 = 444 3 111 = 4 . 111 3 111 =  64 . 111 3 111

Vì 81 > 64 và  111 4 > 111 3 nên  81 . 111 4 111 > 64 . 111 3 111

Vậy  333 444 > 444 333

c, Ta có:  21 5 = 3 . 7 15 = 3 15 . 7 15

27 5 . 49 8 = 3 3 5 . 7 2 8 = 3 15 . 7 16

Vì  7 15 < 7 16 nên  3 15 . 7 15 < 3 15 . 7 16

Vậy  21 5 <  27 5 . 49 8

d, Ta có:  3 2 n = 3 2 n = 9 n

2 3 n = 2 3 n = 8 n

Vì 8 < 9 nên  8 n < 9 n n ∈ N *

Vậy  3 2 n >  2 3 n

e, Ta có: 2017.2018 = (2018–1).(2018+1) = 2018.2018+2018.1–1.2018–1.1

=  2018 2 - 1

Vì  2018 2 - 1 < 2018 2 nên 2017.2018< 2018 2

f, Ta có:  100 - 99 2000 = 1 2000 = 1

100 + 99 0 = 199 0 = 1

Vậy  100 - 99 2000 =  100 + 99 0

g, Ta có:  2009 10 + 2009 9 = 2009 9 . 2009 + 1

=  2010 . 2009 9

2010 10 = 2010 . 2010 9

Vì  2009 9 < 2010 9 nên  2010 . 2009 9 <  2010 . 2010 9

Vậy  2009 10 + 2009 9 <  2010 10

\(10^{30}=\left(10^3\right)^{10}=1000^{10}\)

\(2^{100}=\left(2^{10}\right)^{10}=1024^{10}\)

mà \(1024^{10}>1000^{10}\)

\(\Rightarrow10^{30}< 2^{100}\)

Có : \(S=1+2+2^2+2^3+....+2^{99}\)

\(\Rightarrow2S=2+2^2+2^3+....+2^{100}\)

\(\Rightarrow2S-S=\left(2+2^2+2^3+...+2^{100}\right)-\left(1+2+2^2+....+2^{99}\right)\)

\(\Rightarrow S=2^{100}-1< 2^{100}\)

Vậy \(S< 2^{100}\)

 S=1+2+2²+2³+....+2⁹⁹

⇒2S=2+2²+2³+....+2¹⁰⁰

⇒2S−S=2¹⁰⁰-1

S=2¹⁰⁰-1

vì 2¹⁰⁰ -1<2¹⁰⁰

⇒S<2¹⁰⁰

Đặt \(A=1+5^2+5^4+...+5^{40}\)

\(\Rightarrow25A=5^2+5^4+5^6+...+5^{42}\)

Lấy \(25A-A=\left(5^2+5^4+5^6+...+5^{42}\right)-\left(1+5^2+5^4+...+5^{40}\right)\)

\(\Rightarrow24A=5^{42}-1\)

\(\Rightarrow A=\dfrac{5^{42}-1}{24}\)

nguyễn thị hương giang, cúm ơn rất nhìu !!