Ta có :

3x + y - 2x = 14

x : y : z = 3 : 8 : 5 hay \(\frac{x}{3}=\frac{y}{8}=\frac{z}{5}\)

Áp dụng tính chất dãy tỉ số bàng nhau , ta có :

\(\frac{x}{3}=\frac{y}{8}=\frac{z}{5}=\frac{3x}{9}=\frac{2z}{10}=\frac{3x+y-2z}{9+8-10}=\frac{14}{7}=2\)

\(\Rightarrow\hept{\begin{cases}x=2.3=6\\y=2.8=16\\z=2.5=10\end{cases}}\)

TL

Có:

x3=y8=z5=3x9=2z10

Áp dụng tính chất của dãy tỉ số bằng nhau, ta có:

x3=y8=z5=3x9=2z10=3x+y−2z9+8−10=147=2

x3=2⇒x=6x3=2⇒x=6

y8=2⇒y=16

z5=2⇒z=10

HT

no I don't know

Ex1. Find the word which has a different sound in the part underlined. Read the words aloud

1.  A. volunteer           B. committee         C. guarantee                          D. degree

2.  A. chemistry          B. chemical            C. charity                              D. mechanic

3.  A. architect            B. church               C. childhood                         D. change

4.  A. collage               B. cave                   C. cycle  D. cancel

5.  A. child                  B. provide              C. mind  D. think

Ex 2. Find which word does not belong to each group.

     1.  A. environment      B. bank                  C. community                       D. neighbourhood

     2.  A. students             B. homework         C. blood        D. tutors

     3.  A. orphan               B. grandparents      C. nursing home D. elderly

     4.  A. rubbish              B. donate                C. collect                               D. money

     5.  A. green                 B. trees                   C. plant  D. collect

Ex3.   Choose A, B, C or D for each gap in the following sentences

     1.  He ate a lot of fried food so he              fat quickly.

          A. get                     B. got                     C. gets    D. will get

     2.  The Japanese eat a lot offish and healthy food,         they live for a long time.

          A. so                      B. because              C. or  D. but

     3.  Lan               English for more than a year but she can speak it very well.

          A. learns                 B. learn                  C. learned                              D. has learned

     4.  You should watch less TV because looking at screens in a long time    your eyes.   

A. hurt         B. hurts        C. is hurting         D. to hurt

     5.  Go Green               people to recycle rubbish, such as glass, cans and paper.

          A. to encourage      B. encourage          C. encouraged                       D. has encouraged

     6.  Be a Buddy has                 education for street children.

          A. given                 B. spent                  C. provided                           D. helped

     7.  He                 books for poor children for years.

          A. has collected     B. collects              C. is collecting                         D. collected

     8.  Linh often uses her headphones when she listens to music                       her parents don’t loud noise.     

A. so          B. but C. because   D. and

     9.  Ngoc loves              outdoors with trees and flowers.

          A. to be                  B. be                      C. being       D. A & C

     10. I think 10 years from now more people                     going to work by bicycle.

                     A. to enjoy   B. will enjoy          C. enjoying  D. enjoy

Ta có : 

\(\frac{a}{6}=\frac{b}{-4}\)

\(\text{Hay }\frac{a+b}{6+\left(-4\right)}\)

\(\Rightarrow\frac{a^2+b^2}{6^2+\left(-4\right)^2}=\frac{5}{20}=\frac{1}{4}\)

\(\frac{a^2+b^2}{6^2+\left(-4\right)^2}=\frac{1}{4}\Rightarrow\frac{a^2+b^2}{6^2+\left(-4\right)^2}=\frac{1}{2}\)

\(\Rightarrow\hept{\begin{cases}\frac{a}{6}=\frac{1}{2}\Rightarrow a=\pm3\\\frac{b}{-4}=\frac{1}{2}\Rightarrow b=\mp2\end{cases}}\)

Kẻ tia Md // BA ( hình vẽ ) => Md // CD ( do AB // CD )

Khi đó ta có :

\(\widehat{B}+\widehat{M_1}=180^o\left(\text{2 góc trong cùng phía}\right)\)

\(\Rightarrow140^o+\widehat{M_1}=180^o\Leftrightarrow\widehat{M_1}=40^o\)

Lại có : 

\(\widehat{M_1}+\widehat{M_2}=80^o\Rightarrow40^o+\widehat{M_2}=80^o\Leftrightarrow\widehat{M_2}=40^o\)

Lại có :

\(\widehat{M_2}+\widehat{D}=180^o\)\(\Rightarrow40^o+\widehat{D}=180^o\Leftrightarrow\widehat{D}=40^o\)

              Vô duyên quá đi 
 Muốn người ta giúp bài mấy phải nói ra chứ 

 I.  

 /id/: visited,started,needed,weighted

  /t/:  asked,stooped,looked,watched,checked

 /d/:  called,filled,measured

 II.  1. (-)   Her mother didn't write a sick note for her.
         (?)  Did her mother write a sick note for her?

     2.  (-) Nam wasn't absent from school yesterday
          (?) Was nam absent from school yesterday?

    3.   (-) I didn't have a bad cold two days ago.
          (?) Did I have a bad cold two days a go?

   4.    (-) Many students didn't catch flu last month.
          (?) Did many students catch flu last month?

  5.      (-) They weren't happy with their life.
           (?) Were they happy with their life?

  6.      (-) He wasn't suggest going out for dinner.

           (?) Did he suggest going out for dinner?

  7.      (-) I wasn't busy last Sunday.

           (?) Were you busy last Sunday?

  8.      (-) We did not enjoy our summer vacation.

           (?) Did you enjoy your summer vacation?

                                                   Chúc bạn học tốt!