Đáp án `+` Giải thích các bước giải `!`
`(\sqrt{7}+\sqrt{5}+\sqrt{3})(\sqrt{7}+\sqrt{5}+\sqrt{3})`
`= (\sqrt{7}+\sqrt{5}+\sqrt{3})^2`
`= [(\sqrt{7}+\sqrt{5})+\sqrt{3}]^2`
`= (\sqrt{7}+\sqrt{5})^2+2. (\sqrt{7}+\sqrt{5}). \sqrt{3}+3`
`= 7+2. \sqrt{7}. \sqrt{5}+5+2. \sqrt{7}. \sqrt{3}+2. \sqrt{5}. \sqrt{3}+3`
`= 7+2\sqrt{35}+5+2\sqrt{21}+2\sqrt{15}+3`
`= (7+5+3)+ 2\sqrt{35}+2\sqrt{21}+2\sqrt{15}`
`= 15+2\sqrt{35}+2\sqrt{21}+2\sqrt{15}`