Shortcut for quadratic expressions taught in Indian schools

GRE Quant Problem Solving
1

Hi!

In the correction of the mini exam number 15 (GRE Mini Exams - GregMat), at the minute 1:09:42, Greg asks an Indian person for a shortcut to solve quadratic equations. I add a screenshot of the precise moment. It is something about dividing c by a, but I cannot find resources online on when this shortcut is valid.

screenshot
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Can someone point me to an online source about this shortcut? Always looking for ways to save time, as it is currently my bigger problem.

Thanks in advance!
Violetta

2

Here’s a link for the same with proof, scroll down to Sum and Product section - https://www.cuemath.com/algebra/roots-of-quadratic-equation/

3

This is formally known as Vieta's formulas - Wikipedia.

4

Thanks a lot! Best of luck with your GRE preparation