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\(x^2 + bx + 9\) If  has two non-real roots, find all possible values of \(b\). Express your answer in interval notation.

 

Thanks, I do not know how to solve this problem.

 Dec 9, 2018
 #1
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IIf we have non-real roots, the discriminant must be < 0

 

In the form

 

ax^2 + bx + c = 0

 

The discriminant is   b^2 - 4ac

 

 

So  b = b     a = 1    and c = 9       ... so.....

 

b^2 - 4 (1) (9)   < 0

 

b^2 - 36 < 0

 

b^2 < 36

 

The interval that makes this true is

 

-6 < b < 6

 

 

cool cool cool

 Dec 9, 2018

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