Select all of the following that are quadratic equations.


1. x2 + 3 x -5 = 0
2. x2 - x = 3 x + 7
3. 5 x - 7 = 0
4. 7 x2 + 14 x = 0
5. x3 - 3 x2 + 1 = 0
6. x - 5 = 9 x + 7