Ta có: 4 - |x - 5| = 0

=> | x - 5 | = 4

<=> x - 5 = 4

       x - 5 = -4

<=> x = 4 + 5

       x = -4 + 5

<=> x = 9

       x = 1

1) x=9 hoặc x=1

2)x=2 hoặc x=8/3

3)x=6 hoặc x=2

\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{2019.2020}\)

\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2019}-\frac{1}{2020}\)

\(A=1-\frac{1}{2020}\)

\(A=\frac{2019}{2020}\)

\(B=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{2017.2019}\)

\(2B=\frac{2}{1.3}+\frac{2}{3.5}=\frac{2}{5.7}+...+\frac{2}{2017.2019}\)

\(2B=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}=\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}\)

\(2B=1-\frac{1}{2019}\)

\(2B=\frac{2018}{2019}\)

\(B=\frac{2018}{2019}:2=\frac{1009}{2019}\)

Bài 1:

a)12,5 x (-5/7) + 1,5 x (-5/7)

=-5/7*(12,5+1,5)

=-5/7*14

=-10

b)(-1/4) x (6|2/11) + 3|9/11 x (-1/4)

=-1/4*(68/11+42/11)

=-1/4*10

=-5/2

c tương tự

d)\(\frac{9^8\cdot4^3}{27^4\cdot6^5}=\frac{\left(3^2\right)^8\cdot\left(2^2\right)^3}{\left(3^3\right)^4\cdot\left(2\cdot3\right)^5}=\frac{3^{16}\cdot2^6}{3^{12}\cdot2^5\cdot3^5}=\frac{3^{16}\cdot2^5\cdot2}{3^{16}\cdot3^1\cdot2^5}=\frac{2}{3}\)

Bài 2:

a)Ta có:

2⁸⁰⁰=(2⁸)¹⁰⁰=256¹⁰⁰

8²⁰⁰=(8²)¹⁰⁰=64¹⁰⁰

Vì 256¹⁰⁰>64¹⁰⁰ =>2⁸⁰⁰>8²⁰⁰

b)Ta có:

12⁴⁵=(12³)¹⁵=1728¹⁵

Vì 625¹⁵<1728¹⁵ =>625¹⁵<12⁴⁵

a) -5/7x(12,5+1,5)=-10

b) -1/4x (6I2/11+3I9/11) = -1/4x 10=-5/2

c) (-7/5 + -3/8 + -3/5+5/8): 2009/2010 = -7/4:2009/2010=-1005/574

d)3^16x 4^3/3^12x 6^5=3^4x4^3x6^5=......

bài 2)

2^800=2^4x200= 15^200> 8^200

=> 2^800>8^200

B) quên cách làm

Bài 1 câu a:

1/-8 + -5/8

= -1/8 - 5/8

= -6/8

= -3/4

Câu b:

-1/21 + -1/28

= -4/84 - 3/84

= - 7/854

Câu c:

-5/9 + 8/15 + -2/11 + 4/-9 + 7/15

= (8/15+ 7/15) - (5/9 + 4/9) - 2/11

= 1 - 1 - 2/11

= 0 - 2/11

= - 2/11

Câu d:

-25/-75 + 17/34 + 121/- 132

= 1/3 + 1/2 - 11/12

= 4/12 + 6/12 - 11/12

= 10/12 - 11/12

= - 1/12

Bài 2a:

51/23 = 5151/2323 = 515151/232323

\(\frac{5151}{2323}\) = \(\frac{5151:101}{2323:101}\) = \(\frac{51}{23}\) (1)

\(\frac{515151}{232323}\) = \(\frac{515151:10101}{232323:10101}\) = \(\frac{51}{23}\) (2)

Từ (1) và (2) ta có:

\(\frac{51}{23}=\frac{5151}{2323}=\frac{515151}{232323}\) (đpcm)

a,12,5x(-5/7)+1,5x(-5/7)

=-125/14+-15/14

=-10

2,2mu800>8 mu 200

6254 lon hon 12

hứa sẽ

hứa sẽ các bạn

a; -2\(x\) - 3.(\(x-17\)) = 34 - 2.( - \(x\) + 25)

    - 2\(x\) - 3\(x\) + 51 = 34 + 2\(x\) - 50

       2\(x\) + 2\(x\) + 3\(x\) = - 34 + 50 + 51

            7\(x\)            = 67

               \(x\)           =  67 : 7

                \(x\)         =  \(\dfrac{67}{7}\)

Vậy \(x\) = \(\dfrac{67}{7}\) 

b; 17\(x\) + 3.(- 16\(x\) - 37) = 2\(x\) + 43 - 4\(x\)

    17\(x\) - 48\(x\)  - 111 =  2\(x\) - 4\(x\) + 43

    - 31\(x\) - 2\(x\) + 4\(x\) = 111 + 43

        - \(x\) x (31 + 2 - 4) = 154

        - \(x\) x (33 - 4) =  154

         - \(x\) x 29 = 154

         - \(x\)         = 154 : (-29)

           \(x\)        = - \(\dfrac{154}{29}\)

          Vậy \(x=-\dfrac{154}{29}\)