Mn giúp e vs ạ. E cảm ơn
View attachment 128743
55. A
56. C
57. [tex]\forall x\in \mathbb{N}:x\geq 0[/tex]
58. [tex]\forall x,y\in \mathbb{R}:x+y=y+x[/tex]
59. C
60. A
61. C
62. A
63. A
64. [tex]\forall a,b\in \mathbb{R};a,b\geq 0:\frac{a+b}{2}\geq \sqrt{ab}[/tex]
65. B
66. A