Question

Cho 5x=3y. Tìm x biết:

    a) 2x- 3y= 8

    b) 3x+ 2y= -15 

Answer 1

a)Từ \(5x=3y\Rightarrow\frac{x}{3}=\frac{y}{5}\Leftrightarrow\frac{2x}{10}=\frac{3y}{15}\)

Áp dụng tc dãy tỉ 

\(\frac{2x}{10}=\frac{3y}{15}=\frac{2x-3y}{10-15}=\frac{8}{-5}\)

\(\Rightarrow\frac{2x}{10}=-\frac{8}{5}\Rightarrow x=-8\)

 

Answer 2

a)

 \(\begin{cases}5x=3y\\2x-3y=8\end{cases}\)\(\Rightarrow2x-5x=8\)\(\Rightarrow x=-\frac{8}{3}\)

Vậy x = - 8 / 3

b)

\(\begin{cases}5x=3y\\3x+2y=-15\end{cases}\)\(\Rightarrow\begin{cases}10x=6y\\9x+6y=-45\end{cases}\)

\(\Rightarrow9x+10x=-45\)

\(\Rightarrow x=-\frac{45}{19}\)

Vậy x = - 45 / 19

Answer 3

b)Từ \(5x=3y\Rightarrow\frac{x}{3}=\frac{y}{5}\Rightarrow\frac{3x}{9}=\frac{2y}{10}\)

Áp dụng tc dãy tỉ 

\(\frac{3x}{9}=\frac{2y}{10}=\frac{3x+2y}{9+10}=\frac{-15}{19}\)

\(\Rightarrow\frac{3x}{9}=-\frac{15}{19}\Rightarrow x=-\frac{45}{19}\)

Answer 4

phần a nhầm r`

Answer 5

a)Từ \(5x=3y\Rightarrow\frac{x}{3}=\frac{y}{5}\Leftrightarrow\frac{2x}{6}=\frac{3y}{15}\)

Áp dụng tc dãy tỉ

\(\frac{2x}{6}=\frac{3y}{15}=\frac{2x-3y}{6-15}=\frac{8}{-9}\)

\(\Rightarrow\frac{2x}{6}=\frac{-8}{9}\Rightarrow x=-\frac{8}{3}\)

Answer 6

thắng dìm hàng

Answer 7

dìm