Question

Which among the following is a cubic polynomial?

• A. $x^3-3x^{-1}+5$
• B. $2x^3+5x^2+6x+1$
• C. $x^2+x+1$
• D. $x^4+3x^3+4x^2-5x+4$

Answer 1

The correct option is B $2x^3+5x^2+6x+1$

A polynomial of degree $3$ is cubic polynomial.
The general form of cubic polynomial is
$a{x}^3+b{x}^2+cx+d,a,b,c,d\in R,a\ne 0$
So,
$2x^3+5x^2+6x+1$ is a cubic polynomial.