437 NHÉ BẠN

HỌC TỐT~~~

số 0 nhé

HT

437

nh bn

hc tốt, mong các bn kì thi sắp tới vượt qua nhé

là 437 nha bn 

\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)...\left(1-\frac{1}{n+1}\right)\)

\(=\)\(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.....\frac{n}{n+1}\)

\(=\)\(\frac{1.2.3...n}{2.3...\left(n+1\right)}\)

\(=\)\(\frac{1}{n+1}\)

ta có : 

\(\text{Ta có : }\frac{2}{x}=\frac{3}{y}\Leftrightarrow\frac{x}{2}=\frac{y}{3}_{\left(1\right)}\)

\(\frac{3}{y}=\frac{4}{z}\Leftrightarrow\frac{y}{3}=\frac{z}{4}_{\left(2\right)}\)

Từ _{( 1 )} và _{( 2 )} ta có :

\(\frac{x}{2}=\frac{y}{3}=\frac{z}{4}\)

Theo bài ra ta có :

\(\frac{x}{2}=\frac{y}{3}=\frac{z}{4};x-y-2z=-18 \)

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

\(\frac{x}{2}=\frac{y}{3}=\frac{z}{4}=\frac{x-y-2z}{2-3-2.4}=\frac{-18}{-13}=\frac{18}{13}\)

\(\Rightarrow\hept{\begin{cases}\frac{x}{2}=\frac{18}{13}\Rightarrow x=\frac{36}{13}\\\frac{y}{3}=\frac{18}{13}\Rightarrow y=\frac{54}{13}\\\frac{z}{4}=\frac{18}{13}\Rightarrow x=\frac{72}{13}\end{cases}}\)

Trả lời : 

1/.............5............. |A. Did you go to the doctor’s?

2/.............8..................| B. Yes, I’m fine now, thanks.

3/..............1.................| C. Were you here last week, Phong?

4/...............4................| D. I had a sore throat and a headache.

5/...............7................ |E. Do you feel better now?

6/................3...............| F. Oh, I’m sorry to hear that. What was wrong?

7/...............6................| G. No, I didn’t. I just stayed in bed.

8/.................2..............| H. No, I wasn’t. I didn’t feel well. 

Đây nhé!

giúp mk vs mình đang cần gấp

TL:

HT

cảm ơn b