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am lúc nào chả nhỏ hơn dương

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:V

a)\({\dfrac{3}{4}}\)số rác dễ phân hủy là

\({\dfrac{3}{4}}\).12=9(kg)

An nhận đc số cây sen đá là:

9:3=3(cây)

b) đội An thu đc số kg rác khó phân hủy là:

 9:\({\dfrac{3}{20}}\)=60(kg)

  Đ/s: a,3 cây

          b,60 kg

\(\dfrac{x+50}{49}+\dfrac{x+2}{48}+\dfrac{x+50}{47}=-1\)

\(\dfrac{x+50}{49}+\left(\dfrac{x+2}{48}+1\right)+\dfrac{x+50}{47}=0\)

\(\dfrac{x+50}{49}+\dfrac{x+50}{48}+\dfrac{x+50}{47}=0\)

\(\left(x+50\right)\left(\dfrac{1}{49}+\dfrac{1}{48}+\dfrac{1}{47}\right)=0\)

\(\Leftrightarrow x=-50\)  Vì \(\left(\dfrac{1}{49}+\dfrac{1}{48}+\dfrac{1}{47}\right)>0\)

Bài 3:

theo đề bài ta có:

\(\left\{{}\begin{matrix}2a-3b=0\\5b-7c=0\\3a-7b+5c=30\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}a=42\\b=28\\c=20\end{matrix}\right.\)

Bài 4: 

Đặt \(\dfrac{x}{4}=\dfrac{y}{5}=\dfrac{z}{6}=k\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=4k\\y=5k\\z=6k\end{matrix}\right.\)

Ta có: \(x^2-2y^2+z^2=18\)

\(\Leftrightarrow16k^2-50k^2+36k^2=18\)

\(\Leftrightarrow k^2=9\)

Trường hợp 1: k=3

\(\Leftrightarrow\left\{{}\begin{matrix}x=4k=4\cdot3=12\\y=5k=5\cdot3=15\\z=6k=6\cdot3=18\end{matrix}\right.\)

Trường hợp 2: k=-3

\(\Leftrightarrow\left\{{}\begin{matrix}x=4k=-3\cdot4=-12\\y=5k=-3\cdot5=-15\\z=6k=-3\cdot6=-18\end{matrix}\right.\)

1 wears - is wearing

2 are watching - watch

3 have - am having

4 are cleaning - clean

5 reads - is reading

1 wears,is wearing

2,are watching, watch

3,have, am having

4,are cleaning, clean

5,reads, is reading

1 wears,is wearing

2,are watching, watch

3,have, am having

4,are cleaning, clean

5,reads, is reading

 OK

1 C

2 D

3 A

4 A

5 C

6 B

7 A

8 C

9 B

12. C

13. D

14. A

15. A

16. C

17. B

18. D

19. C

20. B

tk mik nha

1.C

2.D

3.A

4.A

5.C

6.B

7.A

8.C

fashion
apparel
Margaretha Ley
Yes, it does
Japan