H\u00ecnh h\u1ecdc – Ch\u01b0\u01a1ng 1 – B\u00e0i 2: Ph\u00e9p \u0111\u1ed1i x\u1ee9ng qua m\u1eb7t ph\u1eb3ng v\u00e0 s\u1ef1 b\u1eb1ng nhau c\u1ee7a c\u00e1c kh\u1ed1i \u0111a di\u1ec7n<\/a><\/blockquote><\/iframe>