Đáp án:
`Q=\frac{2}{4-3sqrt2}-\frac{2}{4+3sqrt2}`
`= -(4+3sqrt2)-[-(4-3sqrt2)]`
`= -4-3sqrt2+4-3sqrt2`
`= -3sqrt2`
$\\$
`P=\frac{sqrt7+sqrt5}{sqrt7-sqrt5}+\frac{sqrt7-sqrt5}{sqrt7+sqrt5}`
`= \frac{(sqrt7+sqrt5)(sqrt7+sqrt5)}{2}+\frac{(sqrt7-sqrt5)(sqrt7-sqrt5)}{2}`
`= \frac{(sqrt7+sqrt5)^2}{2}+\frac{(sqrt7-sqrt5)^2}{2}`
`= \frac{7+2sqrt35+5}{2}+\frac{7-2sqrt35+5}{2}`
`= \frac{12+2sqrt35}{2}+\frac{12-2sqrt35}{2}`
`= \frac{2(6+sqrt35)}{2}+frac{2(6-sqrt35)}{2}`
`= 6+sqrt35+6-sqrt35`
` 12`
$\\$
`Q=sqrt{4+2sqrt3}+sqrt{4-2sqrt2}-\frac{5}{sqrt-2sqrt2}-\frac{5}{sqrt3+sqrt8}`
`= sqrt{(1+sqrt3)^2}+sqrt{4-2sqrt2}-[-(sqrt3+2sqrt2)]-\frac{5}{sqrt3+sqrt8}`
`= 1+sqrt3+sqrt{4-2sqrt2}+sqrt3+2sqrt2-[-(sqrt3-2sqrt2)]`
`= 1+sqrt3+sqrt{4-2sqrt2}+sqrt3+2sqrt2+sqrt3-2sqrt2`
`= 1+3sqrt3+sqrt{4-2sqrt2}`