How to find all rational roots for x^3 - 3x^2 + 4x - 12 = 0?

Bentley Floyd

Bentley Floyd

Answered question

2023-03-12

How to find all rational roots for x 3 - 3 x 2 + 4 x - 12 = 0 ?

Answer & Explanation

Kiara Rollins

Kiara Rollins

Beginner2023-03-13Added 6 answers

x 3 - 3 x 2 + 4 x - 12 = 0 can have one root among factors of 12 i.e. { 1 , - 1 , 2 , - 2 , 3 , - 3 , 4 , - 4 , 6 , - 6 , 12 , - 12 } , if at least one root is rational.
It is apparent that 3 satisfies the equation, hence x - 3 is a factor of x 3 - 3 x 2 + 4 x - 12 . Dividing latter by ( x - 3 ) , we get
x 3 - 3 x 2 + 4 x - 12 = x 2 ( x - 3 ) + 4 ( x - 3 ) = ( x 2 + 4 ) ( x - 3 )
x 2 + 4 = 0 does not have rational rots as discriminant b 2 - 4 a c = 0 - 4 1 4 = - 16
thus the only rational root of x 3 - 3 x 2 + 4 x - 12 = 0 is 3
The two roots will be imaginary numbers - 2 i and + 2 i

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?