g/e^2 - r = m- y add r to both sides
g = m - y + r
__ _________ we can "flip" both fractions and still keep equality...so...
e^2 1
e^2 = 1
____ ________ multiply both sides by g
g m - y + r
e^2 = g / [ m - y + r ] take both roots
e = ±√ [ g / ( m - y + r ) ]
