Bài 1 :
a) ( 2x + 1 )3 = 9.81
=> ( 2x + 1 )3 = 9 . 92
=> ( 2x + 1 )3 = 93
=> 2x + 1 = 9
=> 2x = 9 - 1
=> 2x = 8
=> x = 8 : 2
=> x = 4
Vậy x = 4
a) \(\left(2x+1\right)^3=8.91\)
\(\left(2x+1\right)^3=729\)
\(\left(2x+1^3\right)=9^3\)
\(\Rightarrow2x+1=9\)
\(2x=9-1\)
\(2x=8\)
\(x=8:2\)
\(x=4\)
Vậy \(x=4\) là giá trị cần tìm
b) \(5^x+5^{x+2}=650\)
\(5^x+5^x+5^2=650\)
\(5^x\left(1+5^2\right)=650\)
\(5^x.26=650\)
\(5^x=650:26\)
\(5^x=25\)
\(5^x=5^2\)
\(\Rightarrow x=2\)
Vậy \(x=2\) là giá trị cần tìm
Bài 2
a) ( 3 . 4 . 216 )2 : ( 11 . 213 . 411 - 169 )
= ( 3 . 22 . 216 )2 : [ 11 . 213 . ( 22)11 - ( 24)9 ]
= ( 3 . 218)2 : [ 11 . 213 . 222 - 236 ]
= [ 32 . ( 218)2 ] : [ 11 . 235 - 226 ]
= [ 32 . 236 ] : [ 235(11 - 2 ) ]
= \(\dfrac{3^2.2^{36}}{2^{35}.9}\)
= \(\dfrac{3^2.2}{1.3^2}\)
= 2
Nếu có gì sai , mong bạn thông cảm
b) 5x + 5x+2 = 650
=> 5x + 5x . 52 = 650
=> 5x(1 + 52 ) = 650
=> 5x(1 + 25 ) = 650
=> 5x . 26 = 650
=> 5x = 650 : 26
=> 5x = 25
=> 5x = 52
=> x = 2
Vậy x = 2
(1- 1/2) . ( 1-1/3) . ( 1-1/4).............. (1-1/1999) . (1- 1/2000)
