\(\frac{121212}{161616}-\left(\frac{151515}{323232}-x\right)=2\)

=> \(\frac{3}{4}-\left(\frac{15}{32}-x\right)=2\)

=> \(\frac{15}{32}-x=\frac{3}{4}-2\)

=> \(\frac{15}{32}-x=-\frac{5}{4}\)

=> \(x=\frac{15}{32}-\frac{-5}{4}=\frac{15}{32}+\frac{5}{4}=\frac{55}{32}\)

b) \(\frac{x}{2}+\frac{x}{6}+\frac{x}{12}+\frac{x}{20}+\frac{x}{30}+\frac{x}{42}+\frac{x}{56}+\frac{x}{72}+\frac{x}{90}=\frac{9}{5}\)

=> \(\frac{x}{1\cdot2}+\frac{x}{2\cdot3}+\frac{x}{3\cdot4}+\frac{x}{4\cdot5}+\frac{x}{5\cdot6}+\frac{x}{6\cdot7}+\frac{x}{7\cdot8}+\frac{x}{8\cdot9}+\frac{x}{9\cdot10}=\frac{9}{5}\)

=> \(\frac{x}{1}-\frac{x}{2}+\frac{x}{2}-\frac{x}{3}+...+\frac{x}{9}-\frac{x}{10}=\frac{9}{5}\)

=> \(\frac{x}{1}-\frac{x}{10}=\frac{9}{5}\)

=> \(\frac{10x-x}{10}=\frac{9}{5}\)

=> \(\frac{9x}{10}=\frac{9}{5}\)

=> \(\frac{9x}{10}=\frac{9\cdot2}{5\cdot2}=\frac{18}{10}\)

=> x = 2

64 . 6 + 81 . 4  + 17 . 6

= 384 + 324 + 102

= 708 + 102

= 810

= 64,6+(81,4+17.6)

=64,6+99

=?

\(43.27+93.43+57.61+59.57\)

\(=\left(43.27+93.43\right)+\left(57.61+59.57\right)\)

\(=43\left(27+93\right)+57\left(61+59\right)\)

\(=43.120+57.120\)

\(=120\left(43+57\right)\)

\(=120.100\)

\(=12000\)

Học tốt

43.27+93.43+57.61+59.57=43(27+93)+57(61+59)=43.120+57.120=120(43+57)=120.100=12000

Chúc bạn học tốt

1.plays volleyball                                                                             Ex2.

2.gets up                                                                                         1.No, she doesn't 

3.watches                                                                                        2.Does she get......

4.( bạn ghi nhầm thành 5)                                                               3.Does she go....

5.washes                                                                                          No, she doesn't. She goes to the park every Sunday

6.does

Bạn nhớ kiểm tra lại nhé

1.Zoe.....................every Friday     plays volleyball 

2.She...........................at eleven o'clock every Sunday      gets up

3.She..........................Tv every Friday   watches

5.He....................................his dad's car every Saturday           washes

6.He...................................his homework every Sunday       does

2 Look at exercise 1. Write questions and answers.

1.Does Zoe play volleyball Everyday?

No , she doesn't

2..............she...................at seven o'clock every Saturday? Does / go to the park

No , she doesn't

3...............to the cinema every Sunday?     Does she go

No, she doesn't.

Bài làm:

Ta có: \(A=\frac{5}{4}\div\frac{a}{a+1}=\frac{5}{4}.\frac{a+1}{a}=\frac{5a+5}{4a}\)

\(\Rightarrow4A=\frac{20a+20}{4a}=5+\frac{5}{a}\)

Để 4A là số nguyên

=> \(\frac{5}{a}\inℤ\Rightarrow5⋮a\Rightarrow a\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)

Thử lại để A là số nguyên thì \(a\in\left\{-5;-1\right\}\)

cảm ơn bạn nha, giờ thì mik hiểu rồi!

a) Ta có\(\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+...+\frac{2}{110}=\frac{2}{2.3}+\frac{2}{3.4}+\frac{2}{4.5}+...+\frac{2}{10.11}\)

\(=2\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{10.11}\right)=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{10}-\frac{1}{11}\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{11}\right)=1-\frac{2}{11}=\frac{9}{11}\)

b) Ta có \(1-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-...-\frac{1}{2048}=1-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{2048}\right)\)(1)

Đặt S = \(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}+\frac{1}{2048}\)

=> \(2S=1+\frac{1}{2}+\frac{1}{4}+...+\frac{1}{1024}\)

Lấy 2S trừ S ta có :

2S - S \(=\left(1+\frac{1}{2}+\frac{1}{4}+...+\frac{1}{1024}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}+\frac{1}{2048}\right)\)

\(S=1-\frac{1}{2048}\)

Khi đó (1) <=> \(1-\left(1-\frac{1}{2048}\right)=1-1+\frac{1}{2048}=\frac{1}{2048}\)

\(a,\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+\frac{2}{30}+....+\frac{2}{90}+\frac{2}{110}\)

\(=2.\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+.....+\frac{1}{90}+\frac{1}{110}\right)\)

\(=2.\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+....+\frac{1}{9.10}+\frac{1}{10.11}\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-....+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{11}\right)\)

\(=1-\frac{2}{11}\)

\(=\frac{9}{11}\)

Last year my brother spent his holiday in Da Lat

Chúc bạn học tốt

Bài làm :

- Last year my mother ( spend ) spent his holiday in Đa Lat .

Học tốt

Trả lời:

a,\(24,5\times4,8\)

\(=117,6\)

b,\(\frac{2}{5}\times\frac{1}{2}-\frac{2}{5}\times\frac{1}{3}-\frac{2}{5}\times\frac{1}{6}\)

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

\(=\frac{2}{5}\times0\)

\(=0\)

c,\(0,5\times\left(x-\frac{15}{2}\right)\div\frac{1}{2}=\frac{9}{2}\)

\(\Leftrightarrow\frac{1}{2}\times\left(x-\frac{15}{2}\right)=\frac{9}{4}\)

\(\Leftrightarrow x-\frac{15}{2}=\frac{9}{2}\)

\(\Leftrightarrow x=12\)

Vậy \(x=12\)

Trả lời:

a,\(17-2\times\left(x-9\right)=5\)

\(\Leftrightarrow2\times\left(x-9\right)=12\)

\(\Leftrightarrow x-9=6\)

\(\Leftrightarrow x=15\)

Vậy \(x=15\)

b,\(\frac{7}{3}-\frac{1}{3}\times x=1\)

\(\Leftrightarrow\frac{1}{3}\times x=\frac{4}{3}\)

\(\Leftrightarrow x=4\)

Vậy \(x=4\)

c,\(x+x\div0,25+x\div0,25+x\div0,25=0,45\)

\(\Leftrightarrow x+x\times4+x\times4+x\times4=0,45\)

\(\Leftrightarrow x\times\left(1+4+4+4\right)=0,45\)

\(\Leftrightarrow x\times13=0,45\)

\(\Leftrightarrow x=\frac{9}{260}\)

Vậy \(x=\frac{9}{260}\)

tyugyyuehsyfu7ifhytfcduf7yiftf9r9diujtirorud

Trả lời:

a,\(105,6-x=29,04\)

\(\Leftrightarrow x=76,56\)

Vậy \(x=76,56\)

b,\(x\div7=4,5\times3\)

\(\Leftrightarrow x\div7=13,5\)

\(\Leftrightarrow x=\frac{27}{14}\)

Vậy \(x=\frac{27}{14}\)

c,\(x\times2,8+5,2\times x=48\)

\(\Leftrightarrow x\times\left(2,8+5,2\right)=48\)

\(\Leftrightarrow x\times8=48\)

\(\Leftrightarrow x=6\)

Vậy \(x=6\)