Rearranging the hyperbola equation 625y^2 - 1600x^2 = 1000000
(25y)^2 - (40x)^2 = 1000^2
(25y/1000)^2 - (40x/1000)^2 = 1
(y/40)^2 - (x/25)^2 = 1
By property of hyperbola, the semi-major axis length=40
so at the closest, the houses are 40*2 = 80 yards apart
