a.4/7 < 7/4           b.13/15 > 13/16             c.11/20 < 9/10

a,4/7<7/4

b,13/15>13/16

c,11/20<9/10

so sanh phan so 13/15va 13/16; 11/20va 9/10

Bài đâu hở bạn?

Bài 2: 

c: Để hai đường thẳng song song thì m-1=2

hay m=3

https://dethihsg.com/de-thi-hoc-sinh-gioi-phong-gđt-hoang-hoa-2014-2015/

Mk cảm ơn bạn nha Akari ❤❤❤

ko có gì đâu, chuyện nên lm mà>.<

Đặt x/2 = y/3 = z/5 =k => x= 2k ; y=3k; z=5k

(thay vào => tìm ra k => thay k vào x=2k;y=..... để tính x,y,z)

Dặt x/2=y/3=z/5=k

suy ra x=2k  y=3k  z=5k 

suy ra x.y.z=2k.3k.5k=30k^3

suy ra 30.k^3=120

suy ra k^3=4

roi ban tu lam tiep nha

Đặt x/2 = y/3 = z/5 = k ( k thuộc Q)

=> x = 2k ; y = 3k ; z = 5k

=> x.y.z = 120 

<=> 2k . 3k .5k = 120

<=> 30 .k^3   = 120

<=>   k^3   = 4    (*)

=> k ko tồn tại t/m (*)

=> x ;y ;z vô nghiệm

|x+2|=10

x+2=10

x=10+2

x=8

\(\Leftrightarrow\orbr{\begin{cases}x+2=10\\x+2=-10\end{cases}}\) \(\Leftrightarrow\orbr{\begin{cases}x=10-2=8\\x=-10-2=-12\end{cases}}\)

Vậy \(x\in\left\{-12;8\right\}\)

x + 2 = 10

x      = 8

Khi ta có :

-x - 2 = 10

 x     = 12

Có /x+3/ > 0 hoặc =0 ,tương tự với /x+4/ và /x+5/ nên tổng của chúng cũng lớn hơn hoặc bằng 0

Suy ra 2x lớn hơn hoặc bằng 0

Suy ra x lớn hơn hoặc bằng 0

Suy ra /x+3/+/x+4/+/x+5/=x+3+x+4+x+5=3x+12 mà tổng ban đầu bằng 2x

Suy ra 3x+12 =2x

Suy ra 3x =2x-12 (vô lí với x lớn hơn hoặc bằng 0)

16 If you don't go right now, you will be late for the train

17 If she weren't often absent from class, she could keep peace with her classmates

18 If I had known Alice'saddress, I could have written to her

19 If it hadn't rained, everybody would have gone outdoors

20 If I hadn't been busy, I would have watched TV

21 If people see the UFO, they will call the National UFO Reporting Center

22 If Thu could swim, she would go swimming in Lam Son Swimming pool

23 If his flight hadn't been delayed, he could have been there on time

24 If it hadn't been for Lisa's report, I wouldn't have been able to finish the project

25 If it hadn't been for your help, I could have overcome the problem

26 If she had seen the signal, she would have stopped her car

27 If you didn't spoke too fast, they could understand

28 If he had enough qualifications, he would apply for the job

29 If she polished his shoe, she would look smart

30 If you don't go right now, you will be late for the train