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# Help: Factorization

How is the following equation possible?

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

I forgot

Note by Jason Chrysoprase
1 year, 3 months ago

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

Its not something to memorize to forget though :P · 1 year, 3 months ago

Thanks Nihar, it was quite helpful. · 1 year, 3 months ago

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

How did you get those red numbers ? · 1 year, 3 months ago

So that we can factor out $$(x-4)$$ from each pair. · 1 year, 3 months ago

thx mate · 1 year, 3 months ago

I'm felling silly now XD

I'm 13 · 1 year, 3 months ago