Let U be the set of real numbers. Determine the truth value of the following propositions.
(a) (∀x)(∀y)(x2 + y ≥ 0). (b) (∃x)(∀y)(x2 + y ≥ 0) (c) (∃x)(∀y)(x2 + y2 = 1) (d) (∃x)(∀y)(x ≤ y2)
(e) (∀x)(∃y)(x · y = 1) (f) (∃x)(x2)=2
(g) (∀x)(∃y)(x2 = y) (h) (∃x)(∀y)(xy = 0)
(i) (∃x)(∃y)(x + y ̸= y + x)
(j) (∃x)(∃y)[(x+2y=2)∨(4y+2x=5)] (k) (∃x)(∃y)[(x+y=2)∧(−y+2x=1)]