Analyzing Roots

Algebra Level 1

Determine the nature of the roots of the polynomial y = 3 x 2 5 x + 3 y=3x^2-5x+3

2 2 distinct real roots 1 1 repeated imaginary root 2 2 distinct imaginary roots 1 1 repeated real root

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4 solutions

Trevor B.
Sep 25, 2014

The discriminant D D of a quadratic is equal to b 2 4 a c , b^2-4ac, where the quadratic is equal to a x 2 + b x + c . ax^2+bx+c.

Here, a = 3 , a=3, b = 5 , b=-5, and c = 3. c=3. Plugging in values, D = ( 5 ) 2 4 × 3 × 3 = 25 36 = 11 < 0. D=(-5)^2-4\times3\times3=25-36=-11<0. If the discriminant of a quadratic is less than 0 , 0, then the quadratic has 2 distinct non-real roots \boxed{\text{2 distinct non-real roots}}

Note that an imaginary number is a complex number of the form b i bi , i.e. the real part is 0. What you mean is "2 distinct non-real roots".

Jon Haussmann - 6 years, 8 months ago

Try to prove this: There does not exist a quadratic with real coefficients that has 2 2 non-distinct \textbf{non-distinct} imaginary roots.

Trevor B. - 6 years, 8 months ago

@Victor Loh wrote about the discriminant of a quadratic on the new Brilliant Wiki here . Check it out!

Trevor B. - 6 years, 8 months ago
Aman Gautam
Sep 25, 2014

just look out for the discriminant b^2 - 4ac since it comes out to be negative,we get both the roots imaginary and distinct.

Imaginary root are always district but complimentary. Roots are imaginary since
5 2 4 3 3 < 0 5^2 -4*3*3< 0 .

Aaron Paul
Sep 25, 2014

for y=ax^2+bx+c D>b^2-4ac for real roots of x for y=3x^2-5x+3 D>25-4(3)3 D>25-36 D>(-11) is not true hence booth roots are imaginary and distinct

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