1. `(\sqrt(2x) + \sqrt(8y) )^2 = \sqrt(2x)^2 + 2.\sqrt(2x.8y) + \sqrt(8y)^2`
`= 2x +8\sqrtxy + 8y (x;y≥0)`
2. `(x/2 -2y)^2 = (x/2)^2 - 2. x/2 .2y + (2y)^2 = (x^2)/4 - 2xy + 4y^2 = 4y^2`
3. `(x+1/6 y + 3)^2 = x^2 + (1/6 y)^2 + 3^2 + 2x. 1/6 y + 2x.3 + 2. 1/6 y .3`
`= x^2 + 1/36 y^2 + 9 + 1/3 xy + 6x + y`