Accepted Answer
3x² - 21Factor 3 from both terms:3 (x² - 7)To me, that's as far as you should need to go. But if you want to get completely carried away, you could go one step further, since you have the difference of two squares:3 (x + √7) (x - √7)Of course, there's no end now, because the last binomial could beconsidered another difference of two squares, so you'd have to factor that too:3 (x + √7) (√x + ⁴√7) (√x - ⁴√7)but to me, this would be nonsense.
Suggested Answer
[tex]3x^2-21=3(x^2-7)=3[x^2-(\sqrt7)^2]=3(x-\sqrt7)(x+\sqrt7)[/tex]
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