nguyên tố chỉ có 2 ước 1 và chính nó

ước chung là 1 một của chúng có ước giống nhau

( 2x - 1 )\(^2\) = 64

=> ( 2x -1 )\(^2\) = 8\(^2\) ( Hoặc -8\(^2\) )

Trường hợp 1 :

Nếu ( 2x - 1 )\(^2\) = 8\(^2\)

=> 2x - 1 =8

=> 2x = 9

=> x = 9 : 2

=> x = 4,5

Trường hợp 2 :

Nếu ( 2x -1 ) \(^2\) = ( -8 )\(^2\)

=> 2x ( -1 ) = -8

=> 2x = ( -8 ) + 1

=> 2x = 7

=> x = 7 : 2

=> x = 3,5

Vậy : x = 3,5 hoặc x = 4,5

1 . Tính

a . \(\dfrac{1}{1.2}\) + \(\dfrac{1}{2.3}\) + ... + \(\dfrac{1}{9.10}\)

= 1 - \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) - \(\dfrac{1}{3}\) + ... + \(\dfrac{1}{9}\) - \(\dfrac{1}{10}\)

= 1 - \(\dfrac{1}{10}\)

= \(\dfrac{9}{10}\)

b . \(\dfrac{1}{1.2}\) + \(\dfrac{1}{2.3}\) + \(\dfrac{1}{3.4}\) + ... + \(\dfrac{1}{99.100}\)

= 1 - \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) - \(\dfrac{1}{3}\) + \(\dfrac{1}{3}\) - \(\dfrac{1}{4}\) + ... + \(\dfrac{1}{99}\) - \(\dfrac{1}{100}\)

= 1 - \(\dfrac{1}{100}\)

=\(\dfrac{99}{100}\)

2 . Tìm x , biết :

a . \(\dfrac{2}{5}\) + \(\dfrac{4}{5}\)x - \(\dfrac{7}{5}\) = \(\dfrac{9}{5}\)

\(\dfrac{2}{5}\) - \(\dfrac{7}{5}\) + \(\dfrac{4}{5}\)x = \(\dfrac{9}{5}\)

-1 + \(\dfrac{4}{5}\)x = \(\dfrac{9}{5}\)

\(\dfrac{4}{5}\)x = \(\dfrac{9}{5}\) + 1 ( Quy tắc chuyển vế )

\(\dfrac{4}{5}\)x = \(\dfrac{14}{5}\)

=> 4.x = 14

=> x = 14 : 4

=> x = 3,5

b . \(\dfrac{2}{5}\)x - \(\dfrac{6}{4}\) = \(\dfrac{8}{5}\)

\(\dfrac{2}{5}\)x = \(\dfrac{8}{5}\) + \(\dfrac{6}{4}\)

\(\dfrac{2}{5}\)x = \(\dfrac{31}{10}\)

x = \(\dfrac{31}{10}\) : \(\dfrac{2}{5}\)

x = \(\dfrac{31.5}{10.2}\)

x = \(\dfrac{31.1}{2.2}\)

x = \(\dfrac{31}{4}\)

3 . 27 - 19 + 2010\(^0\)

= 3 . 27 - 19 +1

= 81 - ( 19 -1 )

= 81 - 18

= 63

Đúng cho mình nha ! Thanks !

7\(^x\) . 5 + 49\(^x\) . 2 = 4301.7

7\(^x\) . 4 + ( 7\(^{2^{ }}\) )\(^x\) . 2 = 30107

7\(^x\) . 4 + 7\(^x\) . 2 + 7\(^x\) = 30107

7\(^x\) . ( 4+2+1 ) = 30107

7\(^x\) . 7 = 30107

7\(^x\) = 30107 : 7

7\(^x\) = 4301

=> x ko thuộc giá trị nào