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."
... generalizations) with a being non-zero. These solutions are also called the roots of the equation. The formula reads
<math>
x=\frac{-b \pm \sqrt ...