Đáp án: $P=\dfrac{3}{2}$
Giải thích các bước giải:
Ta có:
$x+2y=0\to x=-2y$
Mà $xy=-6\to -2y\cdot y=-6\to y^2=3$
$\to P=\left(\dfrac{x}{4}\right)^2+\left(\dfrac{y}{2}\right)^2$
$\to P=\left(\dfrac{-2y}{4}\right)^2+\left(\dfrac{y}{2}\right)^2$
$\to P=\left(\dfrac{-y}{2}\right)^2+\left(\dfrac{y}{2}\right)^2$
$\to P=\dfrac{y^2}{4}+\dfrac{y^2}{4}$
$\to P=\dfrac{y^2}{2}$
$\to P=\dfrac{3}{2}$