Question

Tìm x biết

x^2 + 5y^2 -2xy +4x -8y +5=0

Answer 1

x² + 5y² - 2xy + 4x - 8y + 5 = 0

<=> (x² - 2xy + y²) + 4(x - y) + 4 + (4y² - 4y + 1) = 0

<=> (x - y)² + 4(x - y) + 4 + (2y - 1)² = 0

<=> (x - y + 2)² + (2y - 1)² = 0

<=> \(\hept{\begin{cases}x-y+2=0\\2y-1=0\end{cases}}\)

<=> \(\hept{\begin{cases}x=2-y\\y=\frac{1}{2}\end{cases}}\)

<=> \(\hept{\begin{cases}x=2-\frac{1}{2}=\frac{3}{2}\\y=\frac{1}{2}\end{cases}}\)