What two positive real numbers whose product is 50 have the smallest possible sum?

X * y = 50
y = 50 / x
S = x + y = x + 50 / x
S` = 1 - 50 / x²
1 - 50 / x² = 0
50 / x² = 1
x² = 50
x = √ 50 = 5 √2
y = 50 / 5√2 = 5 √2

Those numbers are: x = 5√2 and y = 5√2.