Tìm x, y biết : x/-3 =y/7 và x^2 - y^2 = 360 Ai làm nhanh mk sẽ cho CTLHN và 5 sao nha! Mong mn giúp mình mai mk kiểm tra rồi !

142825543879145

2 năm trước

Loga Sinh Học lớp 12

0 lượt thích 13 xem

1 trả lời

Thích Trả lời

163343778404885

Đặt $\frac{x}{- 3} = \frac{y}{7} = k \Rightarrow \hept {\begin{cases} x = - 3 k \\ y = 7 k \end{cases}$ $\frac{x}{- 3} = \frac{y}{7} = k \Rightarrow \hept {\begin{cases} x = - 3 k \\ y = 7 k \end{cases}$

$\frac{x}{- 3} = \frac{y}{7} = k \Rightarrow \hept {\begin{cases} x = - 3 k \\ y = 7 k \end{cases}$

Khi đó x² - y² = -360

<=> (-3k)² - (7k)² = -360

=> 9k² - 49k² = -360

=> -40k² = -360

=> k² = 9

=> k = $\pm$ 3

Khi k = 3 => x = -9 ; y = 21

Khi k = -3 => x = 9 ; y = -21

Vậy các cặp (a,b) thỏa mãn là (-9 ; 21) ; (9 ; -21)

Vote (0) Phản hồi (0) 2 năm trước

trinhthilannhung14062003

Ta có:

`x/-3=y/7`

`=>x^2/9=y^2/49`

Áp dụng tính chất của dãy tỉ số bằng nhau, ta có:

`x^2/9=y^2/49=(x^2-y^2)/(9-49)=360/-40=-9`

Với `x^2/9=-9`

`=>x^2=-81`

`=>` $\left[ \begin{array}{l}x=9\\x=-9\end{array} \right.$

Với `y^2/49=-9`

`=> y^2=-441`

`=>` $\left[ \begin{array}{l}x=21\\x=-21\end{array} \right.$

Vậy `(x;y)=(81;21),(-81;-21)`

Vote (0) Phản hồi (0) 2 năm trước

Các câu hỏi liên quan

Câu này ra 36 đúng k vậy nếu sai thì các bạn làm lại hộ mik vs

125$m^{2}$ = ............. $km^{2}$

Giúp mik với+giải thích Mik vote cao+5 sao+ctlhn

Mark the letter A, B, C or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions. Question 31 : I have not met her for three years. A. The last time I met her was three years ago. B. It is three years when I will meet her. C. I did not meet her three years ago. D. During three years, I met her once. Question 32 : John, whose cough is terrible, needs to see a doctor. A. John’s terrible cough prevents from seeing a doctor. B. John need to see a doctor because of his terrible cough. C. John’s doctor does not want to see him because he has a bad cough. D. John’s terrible cough forces him to see a doctor. Question 33 : I am very interested in the book you lent me last week. A. The book is interesting enough for you to lend me last week. B. It was the interesting book which you lent me last week. C. The book which you lent me last week is too interesting to read. D. The book that you lent me last week interests me a lot. Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions. Question 34: No member in the team came to his birthday party. But Julia did come. A. Julia was the only member in the team to come to his birthday party. B. Not only did Julia come to his birthday party but also other members did. C. Julia was one of the members who came to his birthday party. D. Every member in the team came to his birthday party. Question 35: What happened in class yesterday is being investigated. But we haven’t figured out. A. We don’t know what could be worked out in class yesterday. B. What to figure out in class yesterday haven’t been done. C. What happened in class yesterday hasn’t been figured out yet. D. We haven’t found out the happening class yesterday.

Giải giúp mình câu b với mình đang cần gấp

Tìm ảnh của vật hình F hộ mik vs

Giúp mk với mn ơi!!!!!!!!!!!!!!!!!!!!!!!!!

Cho mình biết từ nào là từ ghép từ nào là từ láy với

giúp đi please x2 , hay nhất đây

Em hãy kể một kỉ niệm khó quên về tình bạn(Càng dài càng nhiều sao nha mn:3)

Loga.vn - Cộng Đồng Luyện Thi Trực Tuyến