From square of b, take 4ac;
Square root extract, and b subtract;
Divide by 2a; you’ve x, hooray!

I am not sure of the origins of this mnemonic. The earliest version I could find was from J. S. Mackay in 1894, but he says the mnemonic was given to him by a member of the Edinburgh Mathematical Society.

Here’s another mnemonic for the quadratic formula:

The negative Boy (-B) couldnt decide (+/-) if he wanted to go to the rad (√) party. Becuase he was square, (B^2), he missed out (-) on 4 Awesome Chicks. (4 (a)(c). It was all over at 2 AM. -B+/-√B^2-4(a)(c)
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2(a)

[…] Yesterday, I blogged about a mnemonic for learning the quadratic equation. Here is an excellent video that teaches a general mnemonic technique for formula memorization: […]

The negative Boy (-B) couldnt decide (+/-) if he wanted to go to the rad (√) party. Becuase he was square, (B^2), he missed out (-) on 4 Awesome Chicks. (4 (a)(c). It was all over at 2 AM. -B+/-√B^2-4(a)(c)

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2(a)