Question

 bài 1 

cho tỉ lệ thức :

\(\frac{3x-y}{x+y}=\frac{3}{4}\) .tính \(\frac{x}{y}\)

bài 2:

 Tìm x trong tỉ lệ thức

\(\frac{3x+2}{5x+7}=\frac{3x+1}{5x+4}\)

 

Answer 1

bài 1

\(\frac{3x-y}{x+y}=\frac{3}{4}\)

\(\Rightarrow\left(3x-y\right).4=\left(x+y\right)3\)

\(\Rightarrow12x-4y=3x+3y\)

\(\Rightarrow9x=7y\)

\(\Rightarrow\frac{x}{y}=\frac{7}{9}\)

Vậy \(\frac{x}{y}=\frac{7}{9}\)

Answer 2

Answer 3

bài 2

\(\frac{3x+2}{5x+7}=\frac{3x-1}{5x+4}\)

\(\Rightarrow\) \(\left(3x+1\right)\left(5x+4\right)=\left(3x-1\right)\left(5x+7\right)\)

\(\Rightarrow15x^2+12x+10x+8=15x^2+21x-5x-7\)

\(\Rightarrow22x+8=16x-7\)

\(\Rightarrow22x+16x=-7-8\)

\(\Rightarrow6x=-15\)

\(\Rightarrow x=-2,5\)

Vậy x=-2,5

Answer 4

Bài 2 : 

3x+2 /5x+7 = 3x+1 /5x+4 

=> ( 3x+2 ).(5x+4) = (3x+1) . (5x+7) 

15x² + 12x + 10x +8 = 15x² + 21x + 5x +7 

4x=1 

=> x=1/4