`a)`
`(3x+1)^2`
`= (3x)^2 + 2 . 3x . 1 + 1^2`
`= 9x^2 + 6x + 1`
`b)`
`(2-x)^2`
` = 2^2 - 2 . 2 . x + x^2`
`= 4 - 4x + x^2`
`c)`
`(x/2 + 1)^2`
` = (x/2)^2 + 2 . x/2 . 1 + 1^2`
`= (x^2)/4 + x + 1`
`d)`
`(2/3x - y)^2`
` = (2/3x)^2 - 2 . 2/3x . y + y^2`
` = 4/9x^2 - 4/3xy + y^2`
`e)`
`((x^2)/2 + y^2)^2`
`= ((x^2)/2 )^2 + 2 . (x^2)/2 . y^2 + (y^2)^2`
`= (x^4)/4 + x^2 y^2 + y^4`
`f)`
`(4/5x^2 - 2/3y)^2`
` = (4/5x^2)^2 - 2 . 4/5 x^2 . 2/3 y + (2/3y)^2`
` = 16/25 x^4 - 16/15 x^2y + 4/9 y^2`
