`a) x^2(5x^3 – x -1/2)`
`= x^2. 5x^3 +x^2 . (-x) + x^2. (-1/2)`
`= 5x^5 – x^3 – 1/2x^2`
`b) (3xy – x^2 + y)^2 /3x^2y`
`= 2/3x^2y. 3xy +2/3x^2y. (- x^2) + 2/3x^2y. y`
`= 2x^2y^2– 2/3x^4y + 2/3x^2y^2`
`c) (4x^3– 5xy + 2x)(-1/2xy)`
`= -1/2xy . 4x^3 + (-1/2xy) . (-5xy) + (- 1/2xy) . 2x`
`= -2x^4y +5/2x^2y^2 – x2y.`