Find the points on the curve xy 2 = 250 that are closest to the origin.

Hello :
let : M(x,y) in the curve  and  the origin : O (0,0)
calculate : OA
OA² = x²+y².....(1)
but : xy² = 250
so : y² = 250/x
subsct in (1) :
OA² =  x² + 250/x
 let : f(x) = x² +250/x
calculate the minumum of : f
f'(x) = 2x - 250/x²
f'(x) = 0 : 250/x² = 2x
 x^3 = 125 = 5^3
x= 5
f(5) =5² +250/3 =325/3....(The closest distance)

M(x,y) in the curve  : x=5 : 5y² = 250
y² =50
y = √(50) or y = - √(50)
two points on the curve xy 2 = 250 that are closest to the origin:
M1 (5 , √(50))   , M2 (5 , -√(50)) 

Hello,
All we have to do it to minimise