Mixing hyperbola the inverse problem

The simplest inverse approach consists, given the end-member coordinates, in finding the mixing parameters of any individual mixture, i.e., finding the parameter q defined by equation (1.3.1). We will treat this case with an example. 

Let us express 87Sr/86Sr in the mixture as a function of the 86Sr allotments q and the 87Sr/86Sr ratio of each end-member 

Since effects of radioactive decay on the molar mass can be neglected, q bas Sr can be replaced with an excellent precision by pbasSr. Moreover, the definition of q expressed through equation (1.3.2) as a function of mass fractions / and concentrations CSr requires 

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