\(1\)) \(\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{12}{19}\)

\(=\frac{7}{19}\left(\frac{8}{11}+\frac{3}{11}\right)+\frac{12}{19}\)

\(=\frac{7}{19}+\frac{12}{19}\)

\(=1\)

\(2\)) \(\frac{\frac{2}{5}+\frac{2}{7}-\frac{2}{9}-\frac{2}{11}}{\frac{4}{5}+\frac{4}{7}-\frac{4}{9}-\frac{4}{11}}\)

\(=\frac{\frac{2}{5}+\frac{2}{7}-\frac{2}{9}-\frac{2}{11}}{2\left(\frac{2}{5}+\frac{2}{7}-\frac{2}{9}-\frac{2}{11}\right)}\)

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

1. \(\frac{7}{19}\times\frac{8}{11}+\frac{7}{19}\times\frac{3}{11}+\frac{12}{19}\)

\(=\frac{7}{19}\left(\frac{8}{11}+\frac{3}{11}\right)+\frac{12}{19}\)

\(=\frac{7}{19}\times1+\frac{12}{19}=\frac{19}{19}=1\)

2. \(\frac{\frac{2}{5}+\frac{2}{7}-\frac{2}{9}-\frac{2}{11}}{\frac{4}{5}+\frac{4}{7}-\frac{4}{9}-\frac{4}{11}}\)

\(=\frac{\frac{2}{5}+\frac{2}{7}-\frac{2}{9}-\frac{2}{11}}{2\left(\frac{2}{5}+\frac{2}{7}-\frac{2}{9}-\frac{2}{11}\right)}=\frac{1}{2}\)

\(\frac{-4}{7}\times\frac{5}{11}+\frac{-4}{7}\times\frac{6}{11}+\)\(2017\frac{4}{7}\)

\(=\frac{-4}{7}\times\left(\frac{5}{11}+\frac{6}{11}\right)+2017+\frac{4}{7}\)

\(=\frac{-4}{7}\times1+\frac{4}{7}+2017\)

\(=\left(\frac{-4}{7}+\frac{4}{7}\right)+2017\)

\(=0+2017=2017\)

 Since + thời điểm trong quá khứ: since 1992, since May.: kể từ khi

- For + khoảng thời gian: for five days, for five minutes, ….: trong vòng

I haven’t heard from her for 3 months. (Tôi không nghe tin tức gì từ cô ấy trong 3 tháng rồi)

She hasn’t met him since he was a little boy. (Cô ấy không gặp anh ấy kể từ khi anh ấy còn là 1 cậu bé.)

- Already: đã

Dùng trong câu khẳng định hay câu hỏi, ALREADY có thể đứng ngay sau have và cũng có thể đứng cuối câu.

I have already had the answer = I have had the answer already.

Have you typed my letter already?

- Yet: chưa

Dùng trong câu phủ định hoặc nghi vấn. YET thường đứng cuối câu.

Mary hasn’t written her report yet = Mary hasn’t written her report.

I hasn’t decided what to do yet = I hasn’t decided what to do.

Have you read this arle yet? = Have you read this arle?

- Just: vừa mới

Dùng để chỉ một hành động vừa mới xảy ra.

I have just met her.

I have just tidied up the kitchen.

I have just had lunch.

- Recently, Lately: gần đây

She has recently arrived from New York.

- So far: cho đến bây giờ

We haven’t finished the English tenses so far.

- Up to now, up to the present, up to this moment, until now, until this time: đến tận bây giờ.

He hasn’t come up to now.

- Ever: đã từng

- Never… before: chưa bao giờ

I have never eaten a fish before. Have you eaten a fish?

- In/Over/During/For + the + past/last + time: trong thời gian qua

It has rained in the last week.

I haven’t met her over the last 2 months.

- Gone to: đi chưa về

Mary is on holiday. She has gone to France.

–> Có nghĩa là bây giờ cô ấy đang ở đó hoặc đang trên đường đến đó.

- Been to: đi về rồi

Mary has been to France. She is back to England now.

–> Mary đã từng ở Pháp nhưng giờ đã về Anh rồi.

A = 4/3 x 7 + 4/7 x 11 + 4/11 x 15 + .... + 4/95 x 99

A = 4/3 - 4/7 + 4/7 - 4/11 + 4/11 - 4/15 + ..... + 4/95 - 4/99

A = 4/3 - 4/99

A = 128/99

\(A=4\left(\frac{4}{3.7}+\frac{4}{7.11}+.......+\frac{4}{95.99}\right)\)

\(=4\left(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+.......+\frac{1}{95}-\frac{1}{99}\right)\)

\(=4.\left(\frac{1}{3}-\frac{1}{99}\right)\)

\(=4.\left(\frac{33}{99}-\frac{1}{99}\right)\)

\(=4.\frac{32}{99}=\frac{128}{99}\)

\(A=\frac{4}{3}.\frac{4}{7}+\frac{4}{7}.\frac{4}{11}+...+\frac{4}{95}.\frac{4}{99}\)

\(A=4\left(\frac{1}{3}.\frac{1}{7}+\frac{1}{7}.\frac{1}{11}+...+\frac{1}{95}.\frac{1}{99}\right)\)

\(A=4\left(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{95}-\frac{1}{99}\right)\)

\(A=4\left(\frac{1}{3}-\frac{1}{99}\right)\)

\(A=4.\frac{32}{99}\)

\(A=\frac{128}{99}\)

\(\Rightarrow A=\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+...+\frac{4}{95.99}\)

\(A=4\left(\frac{1}{3.7}+\frac{1}{7.11}+\frac{1}{11.15}+...+\frac{1}{95.99}\right)\)

\(A=4.\frac{1}{4}\left(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{15}+...+\frac{1}{95}-\frac{1}{99}\right)\)

\(A=\frac{4}{4}\left(\frac{1}{3}-\frac{1}{99}\right)\)

\(A=\frac{32}{99}\)

\(\frac{4}{3}.\frac{4}{7}+\frac{4}{7}.\frac{4}{11}+\frac{4}{11}.\frac{4}{15}+...+\frac{4}{95}.\frac{4}{99}\)

\(\Leftrightarrow\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{15}+...+\frac{1}{95}-\frac{1}{99}\)

\(=\frac{1}{3}-\frac{1}{99}=\frac{32}{99}\)

\(\Leftrightarrow A=\frac{32}{99}\)

sai rồi

\(=\frac{3\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{11}\right)}{4\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{11}\right)}\)

\(=\frac{3}{4}\)

\(\frac{\frac{3}{5}+\frac{3}{7}-\frac{3}{11}}{\frac{4}{5}+\frac{4}{7}-\frac{4}{11}}\)

\(=\frac{\frac{1}{5}\times3+\frac{1}{7}\times3-\frac{1}{11}\times3}{\frac{1}{5}\times4+\frac{1}{7}\times4-\frac{1}{11}\times4}\)

\(=\frac{3\times(\frac{1}{5}+\frac{1}{7}-\frac{1}{11})}{4\times(\frac{1}{5}+\frac{1}{7}-\frac{1}{11})}\)

\(=\frac{3}{4}\)

Đáp án:\(\frac{3}{4}\)

M= \(\frac{\frac{3}{5}+\frac{3}{7}-\frac{3}{11}}{\frac{4}{5}+\frac{4}{7}-\frac{4}{11}}\)

 =\(\frac{3.\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{11}\right)}{4.\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{11}\right)}\)

=\(\frac{3}{4}\)

tính M giúp em với anh chị ơi

ảm ơn nhék ạ

dễ thôi mà

A\(=1\)

A=\(\frac{5\left(\frac{1}{7}-\frac{1}{9}+\frac{1}{11}\right)}{4\left(\frac{1}{7}-\frac{1}{9}+\frac{1}{11}\right)}\)+\(\frac{1}{4}\)

A=\(\frac{5}{4}+\frac{1}{4}\)

A=\(\frac{6}{4}\)=\(\frac{3}{2}\)

k cho mk nha bn