FUNCTION :  QP2 - The function {x}^2 - {x} + 1/6

CALLING SEQUENCE :  QP2(x)               

PARAMETERS :      x - real number

SYNOPSIS :   Calculates {x}^2 - {x} + 1/6
             Used by v0, vinf, etga, _ETAnm
             Here {x} = fpart(x) = fractional part of x
EXAMPLES :   

>  with(thetaids):
>  _ETAnm(5,1);
                                                1/60
                           JAC(1, 5, infinity) q
                           -------------------------
                              JAC(0, 5, infinity)

>  QP2(1/5);
                                     1/150

>  QP2(1/5 + 1);
                                     1/150

>  QP2(1/5)*5/2;
                                      1/60


SEE ALSO :  v0, vinf, egeta, _ETAnm