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16 tháng 4 2022

(D) bạn nhé mình ko nói dối  ko tin có thể thử lại

17 tháng 4 2022

d

 

10 tháng 11 2021

Kẻ AH⊥BC

ta có: \(VP=AB^2+BC^2-2.AB.BC.cosB=AB^2+BC^2-2.AB.BC.\dfrac{BH}{AB}=AB^2+BC^2-2.BH.BC=AB^2-BH^2+BC^2-2.BH.BC+BH^2=AH^2+\left(BC-BH\right)^2=AH^2+CH^2=AC^2=VT\)

29 tháng 5 2022

She does not go to school at 8 o'clock
He does not have dinner at 9 o'clock
She does not go to bed at 7 o'clock
He does not go home at 4 o'clock
He does not go to bed at 9 o'clock

NV
12 tháng 11 2021

11c.

Từ đề bài ta có:

\(\left\{{}\begin{matrix}\dfrac{16a-b^2}{4a}=\dfrac{9}{2}\\16a+4b+4=0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}2b^2=-4a\\b=-4a-1\end{matrix}\right.\)

\(\Rightarrow2b^2-b=1\Leftrightarrow2b^2-b-1=0\Rightarrow\left[{}\begin{matrix}b=1\Rightarrow a=-\dfrac{1}{2}\\b=-\dfrac{1}{2}\Rightarrow a=-\dfrac{1}{8}\end{matrix}\right.\)

Có 2 parabol thỏa mãn: \(\left[{}\begin{matrix}y=-\dfrac{1}{2}x^2+x+4\\y=-\dfrac{1}{8}x^2-\dfrac{1}{2}x+4\end{matrix}\right.\)

NV
12 tháng 11 2021

4f.

Từ đề bài ta có:

\(\left\{{}\begin{matrix}1+b+c=0\\\dfrac{4c-b^2}{4}=-1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}c=-b-1\\c=\dfrac{b^2}{4}-1\end{matrix}\right.\)

\(\Rightarrow\dfrac{b^2}{4}+b=0\)

\(\Rightarrow\left[{}\begin{matrix}b=0\Rightarrow c=-1\\b=-4\Rightarrow c=3\end{matrix}\right.\)

Có 2 parabol thỏa mãn: \(\left[{}\begin{matrix}y=x^2-1\\y=x^2-4x+3\end{matrix}\right.\)

27 tháng 2 2022

câu 1 ,2 ,3 mk làm đc r nha

 

27 tháng 2 2022

4. achievements

5. competitive

6. climbing

7. player

8. famous

9. information

10. professional

11. competition

12. Congratulation

13. footballer

14. useful

15. loudly

21 tháng 8 2021

1 not going on holiday with you

2 such easy questions that all the students got them right

3 we had had time, we would have visited the museum

4 to Daisy for breaking her vase

5 studying ENglish 5 years ago

6 are thought to be the most popular dance in Brazil

7 sooner had she received the exam result than she phoned her mom

8 It was the absence of leadership that caused most of the problems on the committee

9 you have any complants about the product, return it to the shop

10 The more fondness for the game increased , the more proficiency he has

11 been a dramatical rise in house prices this year

12 believed to have escaped in a stolen car

13 gone out with him for 2 years

14 he was going to meet his sister in front of the station

 
30 tháng 3 2022

sao nó lại mờ thế?

30 tháng 3 2022

nhiều thế này ai mà làm nổi

2 tháng 4 2021

\(1+cota+cot^2a+cot^3a\)

\(=1+\dfrac{cosa}{sina}+\dfrac{cos^2a}{sin^2a}+\dfrac{cos^3a}{sin^3a}\)

\(=\left(1+\dfrac{cosa}{sina}\right)\left(1+\dfrac{cos^2a}{sin^2a}\right)\)

\(=\dfrac{sina+cosa}{sina}.\dfrac{sin^2a+cos^2a}{sin^2a}\)

\(=\dfrac{cosa+sina}{sin^3a}\)