In search of a structure to solve an equation for two variables

Hi all

I have an equation that is like :

M(r) = A * d(f(r))/dr + B * f(r) + C

I want to substitute r with R1 and R2 each time , that in this case there will be two constants in the equation , and then equalize the substitution to zero and find the d1 and d2 ,

where d1 and d2 are the constants

how can I do that in Matlab ? should it be first parametrically then numerical ?