1893 - Thomas Edison received two U.S. patents. The first was for a "Cut Out for Incandescent Electric Lamps" and another for a "Stop Device" (No. 491,992-3). Also No. 492,150 for "Process of Coating Conductors for Incandescent Lamps."
... form of the quadratic formula is not ideal. See Loss of significance for details.
Derivation
The quadratic formula is derived by the method of completing th ...