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!!

Algebra ->  Polynomials-and-rational-expressions -> 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!!       Log On


   

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) About Me  (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!!
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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.