44. c

45. a

46. câu này có vẻ là a

47. b

48. d

49. a

50. cái này bị thiếu đáp án d nên mình hơi phân vân ý

Chọn C và Chọn A

a: Xét ΔCDA vuông tại A và ΔCBA vuông tại A có

CA chug

DA=BA

Do đó:ΔCDA=ΔCBA

b: Ta có: ΔCDB cân tại C

mà CA là đường cao

nên CA là đường phân giác

c: Xét ΔCEI vuông tại E và ΔCFI vuôg tại F có

CI chung

\(\widehat{ECI}=\widehat{FCI}\)

Do đó:ΔCEI=ΔCFI

Suy ra: CE=CF

Xét ΔCDB có CE/CD=CF/CB

nên EF//DB

1) Ta có: \(\sqrt{2x+5}=\sqrt{3-x}\)

\(\Leftrightarrow2x+5=3-x\)

\(\Leftrightarrow2x+x=3-5\)

\(\Leftrightarrow3x=-2\)

hay \(x=-\dfrac{2}{3}\)

2) Ta có: \(\sqrt{2x-5}=\sqrt{x-1}\)

\(\Leftrightarrow2x-5=x-1\)

\(\Leftrightarrow2x-x=-1+5\)

\(\Leftrightarrow x=4\)

3 , \(PT\left(đk:\frac{16}{3}\ge x\ge3\right)< =>x^2-3x=16-3x\)

\(< =>x^2-16=0< =>\left(x-4\right)\left(x+4\right)=0< =>\orbr{\begin{cases}x=4\left(tm\right)\\x=-4\left(ktm\right)\end{cases}}\)

4 , \(PT\left(đk:...\right)< =>2x^2-3=4x-3< =>2x^2-4x=0\)

\(< =>2x\left(x-2\right)=0< =>\orbr{\begin{cases}x=0\left(...\right)\\x=2\left(...\right)\end{cases}}\)

bạn tự tìm đk rồi đối chiếu nhé :P

5, \(PT\left(đk:...\right)< =>\left(2x-7\right)\left(x-2\right)=x-2\)

\(< =>\left(x-2\right)\left(2x-7-1\right)=0\)

\(< =>\orbr{\begin{cases}x=2\\2x-8=0\end{cases}< =>\orbr{\begin{cases}x=2\\x=4\end{cases}}}\)

6, \(PT\left(đk:...\right)< =>x^2-x-6=3x-1\)

\(< =>x^2-4x-5=0< =>\left(x-5\right)\left(x+1\right)=0\)

\(< =>\orbr{\begin{cases}x=5\\x=-1\end{cases}}\)

1) Ta có: \(\sqrt{4x}=\sqrt{5}\)

nên 4x=5

hay \(x=\dfrac{5}{4}\)

2) Ta có: \(\sqrt{16x}=8\)

nên 16x=64

hay x=4

3, \(2\sqrt{x}=\sqrt{9x}-3\left(đk:x\ge0\right)\)

\(< =>2\sqrt{x}-3\sqrt{x}+3=0\)

\(< =>3-\sqrt{x}=0< =>x=9\)(tmđk)

4, \(\sqrt{3x-1}=4\left(đk:x\ge\frac{1}{3}\right)\)

\(< =>3x-1=16< =>3x-17=0\)

\(< =>x=\frac{17}{3}\)(tmđk)

5, \(\sqrt{-3x+4}=12\left(đk:x\le\frac{4}{3}\right)\)

\(< =>-3x+4=144\)

\(< =>-3x-140< =>3x+140=0< =>x=-\frac{140}{3}\)(tmđk)

6, \(\sqrt{2-3x}=10\left(đk:x\le\frac{2}{3}\right)\)

\(< =>2-3x=100< =>3x+98=0< =>x=-\frac{98}{3}\)(tmđk)

1, Nam isn't so short as Hưng

2,Lan drives to work

3,How many fans are there in the classroom ?

4,It took 15 minutes 

5,Unless she work hard ,giữ nguyên

Câu 1:

\(\left(4x+3\right)\left(3x^2+x-2\right)\left(2x^2-3x-5\right)=0\\ \Leftrightarrow\left(4x+3\right)\left(3x-2\right)\left(x+1\right)\left(2x-5\right)\left(x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{3}{4}\\x=-1\\x=\dfrac{2}{3}\\x=\dfrac{5}{2}\end{matrix}\right.\\ \Leftrightarrow A=\left\{-1;-\dfrac{3}{4};\dfrac{2}{3};\dfrac{5}{2}\right\}\)

Câu 2:

\(\left(x^2-4\right)\left(x-3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-2\\x=3\end{matrix}\right.\Leftrightarrow A=\left\{-2;2;3\right\}\\ \left|5x\right|-11\le0\Leftrightarrow\left|5x\right|\le11\Leftrightarrow-11\le5x\le11\\ \Leftrightarrow-\dfrac{11}{5}\le x\le\dfrac{11}{5}\\ \Leftrightarrow B=\left[-\dfrac{11}{5};\dfrac{11}{5}\right]\)

\(\Leftrightarrow A\cap B=\left\{-2;2\right\}\\ A\cup B=\left[-\dfrac{11}{5};3\right]\\ A\B=\left\{3\right\}\)

Câu 6: 

a: Ta có: \(x\cdot\dfrac{3}{2}-3=\dfrac{1}{2}\)

\(\Leftrightarrow x\cdot\dfrac{3}{2}=\dfrac{7}{2}\)

hay \(x=\dfrac{7}{3}\)

b: Ta có: \(\left|2x-1\right|=2\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-1=2\\2x-1=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=3\\2x=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{1}{2}\end{matrix}\right.\)

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1. Let's go to the school cafeteria to have a cold drink.

2. Ba is learning to play the guitar in the music room at the moment.

3. The boy enjoys playing computer games very much.

4. How often do you go to the movies?

5. Nga's favourite pastime is talking with her friends.

6. What about going to Dam Sen water park this weekend?

7. Would you like to come to my house for dinner this evening?

8. American students enjoy playing sports after school.

9. What do you often do in your free time?

10. Some students are playing marbles in the school yard at the moment.