The set of all real numbers $x$ such that $x ^ { 3 } ( x + 1 ) ( x - 2 ) \geq 0$ is: (a) the interval $2 \leq x < \infty$ (b) the interval $0 \leq x < \infty$ (c) the interval $- 1 \leq x < \infty$ (d) none of the above.
(d) Check for 'test points' $-1$, and $1$.
The set of all real numbers $x$ such that $x ^ { 3 } ( x + 1 ) ( x - 2 ) \geq 0$ is:\\
(a) the interval $2 \leq x < \infty$\\
(b) the interval $0 \leq x < \infty$\\
(c) the interval $- 1 \leq x < \infty$\\
(d) none of the above.