Đáp án`+`Giải thích các bước giải:
` d)` `(``7`$\sqrt{32}$ `+2`$\sqrt{18}$ `-2`$\sqrt{8}$ `):`$\sqrt{2}$
`=` `(``7`$\sqrt{16.2}$ `+2`$\sqrt{9.2}$ `-2`$\sqrt{4.2}$ `):`$\sqrt{2}$
`=` `(28`$\sqrt{2}$ `+``6`$\sqrt{2}$ `-4`$\sqrt{2}$ `):`$\sqrt{2}$
`=` `30`$\sqrt{2}$ `:`$\sqrt{2}$
`=` `30`
` f)` ` (` $\sqrt{28}$ `-2`$\sqrt{3}$ `+`$\sqrt{7}$`).`$\sqrt{7}$ `+`$\sqrt{84}$
`=` `(``2`$\sqrt{7}$ `-2`$\sqrt{3}$ `+`$\sqrt{7}$ `).`$\sqrt{7}$ `+``2`$\sqrt{21}$
`=` `(``3`$\sqrt{7}$ `-2`$\sqrt{3}$`).`$\sqrt{7}$ `+``2`$\sqrt{21}$
`=` ` 21 - 2`$\sqrt{21}$ `+``2`$\sqrt{21}$
`=21`
