Answer:
See below
Step-by-step explanation:
(a) There is a number whose cube is equal to 2.
[tex]\large \exists x \in \mathbb{R}\;|\;x^3=2[/tex]
(b) The square of every number is at least 0.
[tex]\large \forall x\in \mathbb{R},\;x^2\geq 0[/tex]
(c) There is a number that is equal to its square.
[tex]\large \exists x \in \mathbb{R}\;|\;x^2=x[/tex]
(d) Every number is less than or equal to its square.
[tex]\large \forall x\in \mathbb{R},\;x\leq x^2[/tex]
(By the way, this last statement is not true when 0 < x < 1)
