`a) sqrt {7 - 4sqrt3}`
`= sqrt{4 - 2. 2sqrt3 + 3}`
`= sqrt{(2 - sqrt3)^2}`
`= |2 - sqrt3|`
`= 2 - sqrt3`
`b) sqrt{21 - 4sqrt5}`
`= sqrt{1 - 2. 2sqrt5 + 20}`
`= sqrt{(1 - 2sqrt5)^2}`
`= |1 - 2sqrt5|`
`= 2sqrt5 - 1`
`e) sqrt {4 + 2sqrt3}`
`= sqrt{1 + 2sqrt3 + 3}`
`= sqrt{(1 + sqrt3)^2}`
`= |1 + sqrt3|`
`= sqrt3 + 1`
`g) sqrt {31 - 10sqrt6}`
`= sqrt{25 - 2. 5sqrt6 + 6}`
`= sqrt{(5 - sqrt6)^2}`
`= |5 - sqrt6|`
`= 5 - sqrt6`
`i) sqrt {x^2 - 2x + 1}`
`= sqrt{(x - 1)^2}`
`= |x - 1|`
