Bài `10:`
`a)` `(\sqrt{7}+\sqrt{3})^2`
`=7+2\sqrt{3.7}+3`
`=10+2\sqrt{21}`
`b)` `(\sqrt{11}-\sqrt{5})^2`
`=11-2\sqrt{11.5}+5`
`=16-2\sqrt{55}`
`c)` `(\sqrt{13}+\sqrt{7})^2`
`=13+2\sqrt{13.7}+7`
`=10+2+\sqrt{91}`
`d)` `(\sqrt{x}+\sqrt{y})^2`
`=x+2\sqrt{xy}+y`
`e)` `(\sqrt{a}-\sqrt{b})^2`
`=a-2\sqrt{ab}+b`
`f)` `(\sqrt{c}+\sqrt{d})^2`
`=c+2\sqrt{cd}+d`
Bài `11:`
`a) ` `(\sqrt{3}+4)(\sqrt{3}+1)`
`=\sqrt{9}+4+4\sqrt{3}+\sqrt{3}`
`=7+5\sqrt{3}`
`b)` `(\sqrt{5}-6)(\sqrt{5}+4)`
`=\sqrt{25}-6\sqrt{5}+4\sqrt{5}-24`
`=-2\sqrt{5}-19`
`c)` `(\sqrt{x}+1)(\sqrt{x}-3)`
`=x+2\sqrt{x}-6-3\sqrt{x}`
`=x-6-3\sqrt{x}`
`d)` `(\sqrt{y}-3)(\sqrt{y}-4)`
`=y+12-3\sqrt{y}-4\sqrt{y}`
`=y+12-7\sqrt{y}`
