Question Details

ax3 + bx2 + cx + d is a polynomial on real x over real coefficients a, b, c, d wherein a ≠ 0. Which of the following statements is true?

Options

A

No choice of coefficients can make all roots identical.

B

a, b, c, d can be chosen to ensure that all roots are complex.

C

d can be chosen to ensure that x = 0 is a root for any given set a, b, c

D

c alone cannot ensure that all roots are real

Show Answer

Correct Answer :

Option C

d can be chosen to ensure that x = 0 is a root for any given set a, b, c

Solution :

Correct Answer: d can be chosen to ensure that x = 0 is a root for any given set a, b, c


Step-by-Step Explanation:


Let us analyze the given cubic polynomial equation with real coefficients:

P(x)=ax3+bx2+cx+d


A value x=x0 is a root of the polynomial P(x) if and only if P(x0)=0.


We want x=0 to be a root of the polynomial. Evaluating P(x) at x=0, we get:

P(0)=a(0)3+b(0)2+c(0)+d

P(0)=d


For x=0 to be a root of P(x), we must have P(0)=0, which implies:

d=0


Regardless of what values are assigned to the coefficients a, b, and c (with a0), simply setting the constant term d=0 guarantees that P(0)=0, thereby making x=0 a root of the polynomial.


Hence, the statement "d can be chosen to ensure that x = 0 is a root for any given set a, b, c" is strictly true.

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