làm bừa thui,ai tích mình mình tích lại

Số số hạng là : 

Có số cặp là :

50 : 2 = 25 ( cặp )

Mỗi cặp có giá trị là :

99 - 97 = 2 

Tổng dãy trên là :

25 x 2 = 50

Đáp số : 50

\(\frac{x-2017}{5}-\frac{x-2017}{6}=\frac{x-2017}{7}-\frac{x-2017}{8}\)

\(\Leftrightarrow\frac{x-2017}{5}-\frac{x-2017}{6}-\frac{x-2017}{7}+\frac{x-2017}{8}=0\)

\(\Leftrightarrow\left(x-2017\right)\left(\frac{1}{5}-\frac{1}{6}-\frac{1}{7}+\frac{1}{8}\right)=0\)

\(\Rightarrow x-2017=0\Rightarrow x=2017\)

Vậy x=2017

giúp mk làm cầu b đi

1.

a) ( x - 3 ) - 8 = -7

x - 3 = -7 + 8

x - 3 = 1

x = 1 + 3

x = 4

b) 10 - x = 5

x = 10 - 5

x = 5

c) 7 - ( 5 + x ) = 2

5 + x = 7 - 2

5 + x = 5

x = 5 - 5

x = 0

d) -x - 8 - 9 = 17

-x - 8 = 17 + 9

-x - 8 = 26

-x = 26 + 8

-x = 34

=> x ko có giá trị

2.

S1 = 1 - 2 + 3 - 4 + 5 - 6 + ... + 2017 - 2018 + 2019

= ( 1 - 2 ) + ( 3 - 4 ) + ( 5 - 6 ) + ... + ( 2017 - 2018 ) + 2019

= ( -1 ) + ( -1 ) + ( -1 ) + ... + ( -1 ) + 2019

S1 có số cặp là : [ ( 2018 - 1 ) : 1 + 1 ] : 2 = 1009 ( cặp )

=> S1 = ( -1 ) . 1009 + 2019

= -1009 + 2019

= 1010

Vậy S1 = 1010

S2 = 1 - 4 + 7 - 10 + ... + 307 - 310 + 313

= ( 1 - 4 ) + ( 7 - 10 ) + ... + ( 307 - 310 ) + 313

= ( -3 ) + ( -3 ) + ... + ( -3 ) + 313

S2 có số cặp là : [( 310 - 1 ) : 3 + 1 ] : 2 = 52 ( cặp )

=> S2 = ( -3 ) . 52 + 313

= ( -156 ) + 313

= 157

Vậy S2 = 157

khó quá bẹn gì đấy ơi

bn ê .; là j vậy

1b)\(\frac{7}{19}x\frac{8}{11}+\frac{3}{11}:\frac{19}{7}-\frac{2}{-19}=\frac{7}{19}x\frac{8}{11}+\frac{3}{11}x\frac{7}{19}+\frac{2}{19}=\left(\frac{8}{11}+\frac{3}{11}\right)\frac{7}{19}+\frac{2}{19}=\frac{7}{19}+\frac{2}{19}=\frac{9}{19}\)

c)\(4\left(\frac{4}{9}+\frac{7}{11}-\frac{4}{9}\right)=4\frac{7}{11}\)

từ rồi làm tiếp

2)

a)\(\frac{5}{6}-x=-\frac{5}{12}-\frac{1}{-4}=-\frac{5}{12}+\frac{1}{4}=-\frac{5}{12}+\frac{3}{12}=-\frac{1}{6}.\)

\(x=\frac{5}{6}--\frac{1}{6}=\frac{5}{6}+\frac{1}{6}=1\)

b)\(\frac{x-2}{-5}=\frac{6}{7}\)

\(\frac{\left(x-2\right)\left(-7\right)}{35}=\frac{30}{35}\)

\(\Rightarrow\left(x-2\right)\left(-7\right)=30\)

c)\(\frac{1}{2}x-\frac{3}{4}x=-\frac{5}{6}\)

\(\left(\frac{1}{2}-\frac{3}{4}\right)x=-\frac{5}{6}\)

\(-\frac{1}{4}x=-\frac{5}{6}\)

\(x=\frac{20}{6}=\frac{10}{3}\)

vậy \(x=\frac{10}{3}\)

a) 2017 x 34 + 2017 x 65 + 2017

= 2017 x ( 34+65+1)

= 2017 x 100

= 201700

b) 3/5 x 7/9 - 3/5 x 2/9

= 3/5 x ( 7/9- 2/9)

= 3/5 x 5/9

= 1/3

a) 2017 x 34 + 2017 x 65 + 2017

= 2017 x (34 + 65 + 1)

= 2017 x 100

= 201700

b) \(\dfrac{3}{5}\) x \(\dfrac{7}{9}\) - \(\dfrac{3}{5}\) x \(\dfrac{2}{9}\)

= \(\dfrac{3}{5}\) x \(\left(\dfrac{7}{9}-\dfrac{2}{9}\right)\)

= \(\dfrac{3}{5}\) x \(\dfrac{5}{9}\)

= \(\dfrac{1}{3}\)

\(a,=2017\times\left(34+65+1\right)=2017\times100=201700\)

\(b,\dfrac{3}{5}\times\left(\dfrac{7}{9}-\dfrac{2}{9}\right)=\dfrac{3}{5}\times\dfrac{5}{9}=\dfrac{15}{45}=\dfrac{1}{3}\)

a) \(19\times\left(52+38\right)-9\times\left(52+38\right)=\)

\(=\)     \(19\times90-9\times90\) 

\(=90\times\left(19-9\right)\) 

\(=90\times10\) 

\(=900\) 

b) \(\dfrac{2}{5}\div\dfrac{3}{7}\times\dfrac{3}{7}\div\dfrac{2}{5}+2019=\)

\(=\left(\dfrac{2}{5}\div\dfrac{2}{5}\right)\times\left(\dfrac{3}{7}\div\dfrac{3}{7}\right)+2019\) 

\(=1\times1+2019\) 

\(=2019\)

19 x ( 52 + 38 ) - 9 x ( 52 + 38 )

= 19 x 90 - 9 x 90

= ( 19 - 9 ) x 90

= 10 x 90

= 900

\(\dfrac{2}{5}:\dfrac{3}{7}\times\dfrac{3}{7}:\dfrac{2}{5}+2019=\left(\dfrac{2}{5}:\dfrac{2}{5}\right)\times\left(\dfrac{3}{7}:\dfrac{3}{7}\right)+2019=1\times1+2019=1+2019=2020\)