Posted by **Chelsi** on Sunday, November 30, 2008 at 7:23pm.

How do you factor 3x^3+81

- Math -
**drwls**, Sunday, November 30, 2008 at 7:30pm
Call it 3(x^3 + 27).

27 is the cube of three, so one root is x = -3 and the corresponding factor is (x+3). For the other factor, use syntheic division to compute

(x^3+27)/(x+3). That turns out to be

(x^2 -3x + 9). The other roots are complex, so leave it as

3x^3 + 81 = 3(x+3)(x^2 -3x + 9)

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