`1, (√x + √y)^2 = x + y + 2√xy`
`2, (√x - √y)^2 = x + y - 2√xy`
`3, x - y = (√x - √y)(√x + √y)`
`4, (√x)^3 + (√y)^3 = (√x + √y)(x - √xy + y)`
`5, (√x)^3 - (√y)^3 = (√x - √y)(x + √xy + y)`
`6, (√x + √y)^3 = (√x)^3 + 3x√y + 3y√x + (√y)^3`
`7, (√x - √y)^3 = (√x)^3 - 3x√y + 3y√x - (√y)^3`