V is the volume of a piramid which is created by the plane

$\displaystyle \frac{x}{\sqrt{x_0}}+\frac{y}{\sqrt{y_0}}+\frac{z} {\sqrt{z_0}}=\sqrt{a}$

and the x=0 y=0 z=0 planes

i cant imagine it

how its a piramid

i know that the volme is base multiplied by height/3

but here i just cant see how tho build the formula for it

in the solution they have done some sort of determinant divided by 6

dont know why