Simplify this way to find Dm/Dy..
(to find Dm/Dy, assuming y=f(x) and m=Dx/Dy...
using variable 'S')
Muliply both sides by 'd'
Now variable use 'S' again to bring 1/m over
Simplify 'y' (using variable 'k')
Now using your 'for instance' result (=> m=2x+3), reduce 'x' by variable 'T' divided by (b/c) and you get the answer.
SST = Dmb/Fck
Does it involve natural logs maybe?
Save your natural logs for Sunday Morning.