Question 138720
ok so i have a factoring polynomials test and im so confued!! the problem is
9b^2-20 i know that its prime but i dont know why its prime! please help!!
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This expression can be factored if you allow irrational numbers in the factors:

9b^2 - 20 = 9b^2 - [sqrt(20)]^2

= (3b-sqrt(20))(3b+sqrt(20))

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Cheers,
Stan H.