\(\frac{4.7-4.5}{64}=\frac{4\left(7-5\right)}{64}\)

                       \(=\frac{4.2}{64}\)

                         \(=\frac{8}{64}\)\(=\frac{1}{8}\)

ko vt lại đề 

=(28-20)/64

=8/64

=1/8

5x-24=51

=>5x=51+24=75 

=>x= 75:5=15

vậy x= 15

4+36:9+x=54

=>4+4+x=54

=>x=54-4-4=46

vậy x=46

a) 5 . x - 24= 1 + 50

    5 . x - 24 = 51

    5 . x        = 51 + 24

    5 . x        = 75

         x        = 75 : 5

         x        = 15

b) 4 + 36 : 9 + x = 54

           36 : 9 + x = 54 - 4

           36 : 9 + x = 50

                  4 + x = 50 

                        x = 50 - 4

                        x = 46

#họctốt

&YOUTUBER&

\(a.\) \(a.b< 0\)

\(\Leftrightarrow a\) và \(b\) là 2 số khác dấu.

Mà: \(a>b\)

\(\Rightarrow\) \(a\) là số âm và \(b\) là số dương.

\(b.\) \(a.b>0\)

\(\Leftrightarrow a\) và \(b\) cùng dấu

Mà: \(a+b< 0\)

\(\Rightarrow a\) và \(b\) là số âm.

vaiiiiiiiiiiiiiiiiiiiiiiiii

Ta có

  \(2^8.4.13=2^9.26\)

  \(2^7.8.65=2^9.130\)

Nên \(2^8.4.13+2^7.8.65=2^9.156\)

  Mà \(2^9:2^9=1\)

        \(156:3=52\)

Do đó A = 52

Đặt tổng trên là A , ta có :

\(\frac{A}{2}=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{98.99}+\frac{1}{99.100}\)

\(\frac{A}{2}=\left(1-\frac{1}{2}\right)+\left(\frac{1}{2}-\frac{1}{3}\right)+\left(\frac{1}{3}-\frac{1}{4}\right)+\left(\frac{1}{4}-\frac{1}{5}\right)+...+\left(\frac{1}{98}-\frac{1}{99}\right)+\left(\frac{1}{99}-\frac{1}{100}\right)\)

\(\frac{A}{2}=\left(1-\frac{1}{100}\right)+\left(\frac{1}{2}-\frac{1}{2}\right)+\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{5}-\frac{1}{5}\right)+...+\left(\frac{1}{98}-\frac{1}{98}\right)+\left(\frac{1}{99}-\frac{1}{99}\right)\)\(\frac{A}{2}=\frac{99}{100}\)

\(A=\frac{99}{100}.2\)

\(A=\frac{99}{50}\)

-x + 6x = (-4)²:8 

  5x=16:8

5x=2

  x=2/5

vậy x=2/5

7+ 2 (5+x) = -9 

2(5+x)=-9-7

2(5+x)=-16

5+x=-16:2

5+x=-8

   x=-8-5

   x=-13

vậy x=-13

-(x- 6)+2(9+x)=17 

-x+6+18+2x=17

-x+2x=17-6-18

x=-7

vậy x=-7 

 2 (x+5) - 4(6-x)= -68

2x+10-24-4x=-68

2x-4x=-68-10+24

-2x= -54

2x=54

  x=54:2

  x=27

vậy x=27      

|x|-58=9

|x|=9+58

|x|=67

=>x=\(\pm\)67

vậy x=\(\pm\)67

\(2x+6< 0\Leftrightarrow2x< -6\Leftrightarrow x< -3\)

Ta có : \(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{512}+\frac{1}{1024}=\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^9}+\frac{1}{2^{10}}\)

Đặ A = \(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^9}+\frac{1}{2^{10}}\)(1)

=> 2A = \(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^8}+\frac{1}{2^9}\)(2)

Lấy (2) trừ (1) theo vế ta có : 

2A - A = \(\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^8}+\frac{1}{2^9}\right)-\left(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^9}+\frac{1}{2^{10}}\right)\)

=> A = \(1-\frac{1}{2^{10}}=\frac{2^{10}-1}{2^{20}}\)

\(A=\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+...+\frac{1}{2^{10}}\)

\(\Leftrightarrow2A=1+\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^9}\)

\(\Rightarrow2A-A=1-\frac{1}{2^{10}}=\frac{1023}{1024}\)