Dr. Loh’s method allows people to calculate the answers without remembering the exact formula. (It also provides a more straightforward proof.)

“Math is not about memorizing formulas without meaning, but rather about learning how to reason logically through precise statements,” Dr. Loh said.

Mr. Wong said Dr. Loh’s version is easier for students because it, “provides one method for solving all kinds of quadratic equations.”

A technique with ancient roots

Dr. Loh delved into mathematics history to find that the Babylonians and Greeks had the same insights, although their understanding was limited because their math was limited to positive numbers. It was only later that people came up with the concepts of negative numbers, zero and even more esoteric concepts like imaginary numbers — the square roots of negative numbers.

He even found out that a math teacher in Sudbury, Canada, named John Savage came up with a similar approach 30 years ago. An article by Mr. Savage in the journal The Mathematics Teacher in 1989 laid out almost the same procedure, although Dr. Loh filled in some nuances of logic in explaining why it works.

“I honestly can’t remember exactly where the eureka moment was,” Mr. Savage said in a phone interview. But it seemed to be an improvement over the usual way of teaching the subject.

He continued using that approach, as did some other teachers he knew. But the internet was still in its infancy, and the idea faded away.