program test_kvadr

implicit none
real(4):: a = 1.0, b = -400.005, c = 2.0
real(4):: x, y, D

D = b*b - 4*a*c
x = (- b + sqrt(d))/2/a
y = (- b - sqrt(d))/2/a
write(*,*) 'x = ', x, ' y = ', y
! x =    400.0000      y =   5.0024572E-03

y = c / x
write(*,*) 'x = ', x, ' y = ', y
! x =    400.0000      y =   4.9999999E-03
end program