Question

Rút gọn: (Giải chi tiết từng bước)

7) \(\left(\sqrt{28}-\sqrt{12}-\sqrt{7}\right)\sqrt{7}+2\sqrt{21}\)

8) \(\left(\sqrt{99}-\sqrt{18}-\sqrt{11}\right)\sqrt{11}+3\sqrt{22}\)

Answer 1

`a, (sqrt 28 - sqrt 12 - sqrt 7) sqrt 7 + 2 sqrt 21`.

`= sqrt(28.7) - sqrt(12.7) - sqrt(7.7) + 2 sqrt 21`.

`= sqrt(4. 7.7) - sqrt (12.7) - 7 + 2 sqrt 21`.

`= 14 - sqrt(4.3.7) - 7 + 2 sqrt 21`.

`= 7`.

`b, (sqrt99-sqrt18-sqrt11)sqrt11+3sqrt22`

`= sqrt(99.11)- sqrt(18.11)-sqrt(11.11) +3sqrt22`

`= sqrt(9.11.11)-sqrt(2.9.11)-11+3sqrt22`

`= 33 - 11 = 22`.