B - C - A - B - B - B - A - A - B - A 
15, A -> DIDN'T GO

B - C - A - B - B - B - A - A - B - A 
15, A -> DIDN'T GO

fashion
apparel
Margaretha Ley
Yes, it does
Japan

Tham khảo!

Xét tứ giác GHKI có 

GH//KI

GH=KI

Do đó: GHKI là hình bình hành

Suy ra: GI=HK

KNJNL

TL:588 tạ nha

588 nhá !

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

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

16C

17A

18B

19D

20C

21C

22A 

16 C

17 A

18 B

19 D

20 C

21 C

22 A 

13, B

14, D

15, C

16, A

13. B ( chắc vậy )

14. D

15. C

16. D

13.B
14.D
15.C
16.A

a: \(A=-\left(\dfrac{4}{9}x-\dfrac{2}{15}\right)^6+5\le5\forall x\)

Dấu '=' xảy ra khi \(x=\dfrac{3}{10}\)

b: \(B=-\left(x-\dfrac{1}{6}\right)^4-\left(2y+1\right)^2\le0\forall x,y\)

Dấu '=' xảy ra khi \(\left(x,y\right)=\left(\dfrac{1}{6};-\dfrac{1}{2}\right)\)