Xu\u1ea5t hi\u1ec7n th\u1ee7 khoa to\u00e0n qu\u1ed1c kh\u1ed1i B \u0111\u1ea1t \u0111i\u1ec3m tuy\u1ec7t \u0111\u1ed1i 30\/30 \u0111i\u1ec3m<\/a><\/blockquote><\/iframe>