How you do cubic? $\pm$

Given that $s$ and $t$ equals

and $p$ and $q$ such that

Manipulating a little bit, $T$ should become

See how $T$ and $S$ have a $\pm$ in them? When you subtract $s$ from $t$ , why does that $\pm$ disappear, and does it equal to the same value as when they have the $\pm$ sign in them?

If you want to see this website, it is: Deriving the Cubic Formula

#Algebra

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Yup, a simpler way to prove that cubic formula is to first depress the cubic polynomial. Cardano's method shows a good illustration of this.

Pi Han Goh - 4 years, 1 month ago

Do you see the last 2 pictures? I was wondering what method allows you to get rid of that $\pm$ sign.

Bloons Qoth - 4 years, 1 month ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$

How you do cubic? ±\pm±

Comments

How you do cubic? $\pm$