ln(1+(0.3915(1-x)/x))=1.59935791078
0.5^-2 minus 12/3 = 0
f(x)=(x-2)/2x-5
(1/x - 1/a) / (x - a)
(1/x - 1/a) / (x + a)
27x+15x = 42x
(3a^2h + 3h^2a + h^3) / h
convert two thirds to decimals
(a+h)^3
(3+x)^3
