SOLUTION: 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!!

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!!

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
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!!
--------------------
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))
=======================
Cheers,
Stan H.

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