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Q.

State whether the following statement is true or false.


If all three zeroes of a cubic polynomial x 3 +a x 2 bx+c   are positive, then at least one of a, b and c is non-negative.


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a

True

b

False 

answer is A.

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Detailed Solution

Given cubic polynomial is m x 3 +n x 2 +lx+q.  
Let’s assume a, b, and c are three roots of the given cubic polynomial.
Then,
a+b+c= n m  
The sum of three positive numbers always gives a positive value, which satisfies the equation a+b+c= n m   if the values of n and m have opposite signs.
And
ab+bc+ac= l m  
The product of two positive number is always positive, which satisfy the equation ab+bc+ca= l m ,   if the signs of c and a are the same.
And
abc= q m   The product of three positive numbers gives a positive value which satisfies the equation abc= q m   if q and m have opposite signs.
So, the signs of coefficients must be different from each other.
Therefore, the given statement is true.
Hence, option (1) is correct.
 

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