Theorem for quadratic equations

[Rayben]

Hi everyone!
Not long ago, I realized a tip to check if the number what you are thinking could be an answer to the equation. If you have a good
intuition you can guess the answer trying faster than if you use the usual way:
The theorem:

1. For positive solutions:

n⋅a+b= (−c)/n  ⟹  X=N

1. For negative solutions:

n⋅a−b= (−c)/n  ⟹  X=−N

PD: (I'm not an English speaker native, so maybe I made some mistakes.)

 

[Dr.Peterson]

Perhaps it will be clearer what you are trying to say if you give a couple examples.

 

[Atum]