Help: Factorization

How is the following equation possible?

$x^3 - 6x - 40 = (x-4)(x^2+4x+10)$

I forgot

#Algebra

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Comments

$x^3-6x-40 \\ = x^3-4x^2+4x^2-16x+10x-40 \\ = x^2(x-4)+4x(x-4)+10(x-4) \\ = (x-4)(x^2+4x+10)$

Its not something to memorize to forget though :P

Nihar Mahajan - 5 years, 1 month ago

I'm felling silly now XD

I'm 13

Jason Chrysoprase - 5 years, 1 month ago

$x^3 - 6x - 40 \\ = x^3 \color{#D61F06}{- 4x^2 + 4x^2 - 16x + 10x} - 40$

How did you get those red numbers ?

Jason Chrysoprase - 5 years, 1 month ago

So that we can factor out $(x-4)$ from each pair.

Nihar Mahajan - 5 years, 1 month ago

@Nihar Mahajan – thx mate

Jason Chrysoprase - 5 years, 1 month ago

Thanks Nihar, it was quite helpful.

Sandeep Bhardwaj - 5 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}`	$\boxed{123}$