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https://www.google.com.vn/search?biw=1366&bih=639&tbm=isch&sa=1&q=airi+li%C3%AAn+qu%C3%A2n+mobile&oq=airi+lien&gs_l=psy-ab.3.0.0l2j0i24k1.8946.10704.0.11832.5.5.0.0.0.0.115.409.4j1.5.0....0...1.1.64.psy-ab..0.5.408...0i67k1.knT-34CDbtQ#imgrc=Lzcrq-JmOyPc2M:

1 + 1 = 1 đôi 

1 + 1 = 2