Bài 5: 

a: Vì (d) đi qua M(-1;3) và N(1;2) nên ta có hệ phương trình:

\(\left\{{}\begin{matrix}-a+b=3\\a+b=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2b=5\\a+b=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}b=\dfrac{5}{2}\\a=2-\dfrac{5}{2}=-\dfrac{1}{2}\end{matrix}\right.\)

Câu 34: \(\overrightarrow{v}=\overrightarrow{AB}+\overrightarrow{DC}+\overrightarrow{BD}+\overrightarrow{CA}\)

\(=\overrightarrow{CA}+\overrightarrow{AB}+\overrightarrow{BD}+\overrightarrow{DC}\)

\(=\overrightarrow{CB}+\overrightarrow{BD}+\overrightarrow{DC}=\overrightarrow{CD}+\overrightarrow{DC}=\overrightarrow{0}\)

=>Chọn D

Câu 33: \(\overrightarrow{OA}+\overrightarrow{OB}=\overrightarrow{CO}+\overrightarrow{OB}=\overrightarrow{CB}\)

=>\(\left|\overrightarrow{OA}+\overrightarrow{OB}\right|=CB=a\)

=>Chọn C

Câu 28: A

Câu 29: D

Câu 30: Gọi AM là đường trung tuyến của ΔABC

ΔABC đều có AM là đường trung tuyến

nên \(AM=BC\cdot\frac{\sqrt3}{2}=\frac{3\sqrt3}{2}\)

Xét ΔABC có AM là đường trung tuyến

nên \(\overrightarrow{AB}+\overrightarrow{AC}=2\cdot\overrightarrow{AM}\)

=>\(\left|\overrightarrow{AB}+\overrightarrow{AC}\right|=2\cdot AM=2\cdot\frac{3\sqrt3}{2}=3\sqrt3\)

=>Chọn D

Câu 1: A

Câu 2: B

Câu 3: D

Câu 4: B

Câu 5: D

Câu 6: A

Câu 7: A

Câu 8: D

Câu 9: D

Câu 10: C

Câu 12: B

Câu 13: A

Câu 14: C

Câu 15: C

Bài 3: 

a: Ta có: \(A=\left(3x+7\right)\left(2x+3\right)-\left(3x-5\right)\left(2x+11\right)\)

\(=6x^2+9x+14x+21-6x^2-33x+10x+55\)

=76

b: Ta có: \(B=\left(x-3\right)\left(x+2\right)-\left(x-5\right)\left(x+4\right)\)

\(=x^2+2x-3x-6-x^2-4x+5x+20\)

=14

cảm ơn bạn

\(M=\sqrt{\dfrac{4}{\left(2-\sqrt{5}\right)^2}}-\sqrt{\dfrac{4}{\left(2+\sqrt{5}\right)^2}}=\dfrac{2}{\left|2-\sqrt{5}\right|}-\dfrac{2}{\left|2+\sqrt{5}\right|}\)

\(=\dfrac{2}{\sqrt{5}-2}-\dfrac{2}{\sqrt{5}+2}=\dfrac{2\left(\sqrt{5}+2\right)-2\left(\sqrt{5}-2\right)}{\left(\sqrt{5}-2\right)\left(\sqrt{5}+2\right)}\)

\(=\dfrac{8}{1}=8\)

Lm ơn giúp mik đii mà mik bt ơn bn đó nhiều lắm . Mik đang rất cần

1 interested in travelling by plane

2 15 minutes riding his bike to school

3 is made by my mother everymorning

4 take care of her little brother

5 able to speak 2 languages when he was young

6 able to play the piano

7 is played all over VN

8 to play voleyball very well when he was young

9 to go fishing when he was young

10 way to the shopping mall

Cảm ơn cậu nhiều lắm ạ 

over

camping

was

couldn't

percussion

takes

look after

go around 

go through

wind

how long

for

do

Cảm ơn cậu nhiều lắm ạ 

Bài 2

a)x-13=-22

x=-22+13

x=-9

b)(2x-8).5=2.5³

(2x-8).5=2.125

(2x-8).5=250

2x-8=250:5

2x-8=50

2x=50+8

2x=58

⇒x=29