`a) (3x+2)^2 = (3x)^2 + 2.3x.2 + 2^2 = 9x^2 + 12x + 4`
`b) (y-1/4)^2 = y^2 - 2. y . 1/4 + (1/4)^2 = y^2 - 1/2y + 1/16`
`c) (x-1/2)^2 = x^2 - 2. x . 1/2 + (1/2)^2 = x^2 - x + 1/4`
`d) (3a^2b + 1/3ab^2)^2`
` = (3a^2b)^2 + 2 . 3a^2b . 1/3ab^2 + (1/3ab^2)^2`
` = 9a^4b^2 + 2a^3b^3 + 1/9a^2b^4`