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sau các phép tính đó thì tổng bao nhiêu vậy bạn ? hình như đề hơi sai
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y + y x 4,5 : 3 + y x 7 : 2 = 255
y + y x 1,5 + y x 3,5 = 255
3y x (1,5 + 3,5) = 255
3y x 5 = 255
3y = 255 : 5
3y = 51
y = 51 : 3
y = 17
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![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{2}{5}\) x y : \(\dfrac{7}{4}\) = \(\dfrac{7}{8}\)
\(\dfrac{2}{5}\) x y = \(\dfrac{7}{8}\) x \(\dfrac{7}{4}\)
\(\dfrac{2}{5}\) x y = \(\dfrac{49}{32}\)
y = \(\dfrac{49}{32}\) : \(\dfrac{2}{5}\)
y = \(\dfrac{245}{64}\)
2\(\dfrac{2}{5}\): y x 1\(\dfrac{1}{4}\) = 2\(\dfrac{3}{5}\)
\(\dfrac{12}{5}\): y x \(\dfrac{5}{4}\) = \(\dfrac{13}{5}\)
\(\dfrac{12}{5}\): y = \(\dfrac{13}{5}\): \(\dfrac{5}{4}\)
\(\dfrac{12}{5}\): y = \(\dfrac{52}{25}\)
y = \(\dfrac{12}{5}\): \(\dfrac{52}{25}\)
y = \(\dfrac{15}{13}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : \(\frac{x}{4}=\frac{y}{7}\)
\(\Rightarrow\frac{x^2}{16}=\frac{y^2}{49}=\frac{3x^2}{48}=\frac{4y^2}{196}=\frac{3x^2-4y^2}{48-196}=\frac{100}{-148}=-\frac{25}{37}\)
Thay vào là ra nhé !:D
Cái chỗ Nguyễn Quang Trung đúng ròi
\(\Rightarrow\hept{\begin{cases}\frac{x}{4}=-\frac{25}{37}\\\frac{y}{7}=-\frac{25}{37}\end{cases}}\Rightarrow\hept{\begin{cases}x=-\frac{100}{37}\\y=-\frac{175}{37}\end{cases}}\)
\(7\text{×}y-y\text{×}2=185\\ \left(7-2\right)\text{×}y=185\\ 5\text{×}y=185\\ y=185:5\\ y=37\)
7×y−y×2=185
(7−2)×y=185
5×y=185
y=185:5
y=37