Question

[Nguyễn Việt Bách]

tìm x;y sao cho x(x-y)=\(\dfrac{3}{10}\) và y(x-y)=\(\dfrac{-3}{50}\)

Answer 1

[Nguyễn Lê Phước Thịnh]

\(x\left(x-y\right)=\dfrac{3}{10}\)

\(y\left(x-y\right)=-\dfrac{3}{50}\)

=>\(\dfrac{x\left(x-y\right)}{y\left(x-y\right)}=\dfrac{3}{10}:\dfrac{-3}{50}=-5\)

=>x/y=-5

=>x=-5y

x(x-y)=3/10

=>\(-5y\left(-5y-y\right)=\dfrac{3}{10}\)

=>\(5y\cdot6y=\dfrac{3}{10}\)

=>\(30y^2=\dfrac{3}{10}\)

=>\(y^2=\dfrac{1}{100}\)

=>\(\left[{}\begin{matrix}y=\dfrac{1}{10}\\y=-\dfrac{1}{10}\end{matrix}\right.\)

TH1: \(y=\dfrac{1}{10}\)

=>\(x=-5y=-5\cdot\dfrac{1}{10}=-\dfrac{5}{10}=-\dfrac{1}{2}\)

TH2: y=-1/10

=>\(x=-5y=-5\cdot\dfrac{-1}{10}=\dfrac{1}{2}\)