Question

Bài 1: Tìm x,y biết:

a.\(\frac{3}{1-2x}\)= \(\frac{-5}{3x-2}\)

b.\(\frac{x}{-3}\) = \(\frac{y}{5}\) và x.y= \(\frac{-5}{27}\)

 

Answer 1

<=> 3.(3x-2) = -5 . (1-2x)

<=> 9x - 6 = -5 - (-10x)

<=> 9x - 10x = -5+6

<=> -x = 1

<=> x = -1

Answer 2

a)\(\frac{3}{1-2x}=\frac{\left(-1\right).5}{\left(-1\right).\left(2-3x\right)}=\frac{5}{2-3x}\)

=>3.(2-3x)=5.(1-2x)

=>6-9x=5-10x

=>10x-9x=5-6

=>x=-1

Answer 3

a) \(\frac{3}{1-2x}=\frac{-5}{3x-2}\)

=>  \(3\left(3x-2\right)=-5\left(1-2x\right)\)

=>  \(9x-6=-5+10x\)

=>  \(-6+5=10x-9x\)

=>  \(-1=x\)  hay  \(x=-1\)

b) \(\frac{x}{-3}=\frac{y}{5}\Rightarrow x=\frac{-3y}{5}\)

Thay vào x . y, ta được:

 \(x\cdot y=\frac{-3y}{5}\cdot y=\frac{-3y^2}{5}=\frac{-5}{27}\)

=> \(27\cdot\left(-3y^2\right)=-5\cdot5\)

=> \(-81y^2=-25\)

=>  \(y^2=-25:\left(-81\right)=\frac{25}{81}\Rightarrow y=\sqrt{\frac{25}{81}}=\frac{5}{9}\)  hoặc  \(y=\frac{-5}{9}\)

y = 5/9      =>   x = \(-\frac{5}{27}:\frac{5}{9}=-\frac{1}{3}\)

y = -5/9       =>   x = \(-\frac{5}{27}:\left(-\frac{5}{9}\right)=\frac{1}{3}\)