This function sets up formulae that are needed at the subsequent stages.
fleishman.roots(p, r)
a vector of length three that contains the Fleishman coefficients.
a vector of length two that contains skewness and kurtosis values.
Fleishman A.I. (1978). A method for simulating non-normal distributions. Psychometrika, 43(4), 521-532.
Param.fleishman