`c) \frac{y}{2x^2 - xy} + \frac{4x}{y^2 - 2xy}`

`= \frac{y}{x(2x - y)} + \frac{4x}{y(y - 2x)}`

`= \frac{y}{x(2x - y)} - \frac{4x}{y(2x - y)}`

`= \frac{y^2 - 4x^2}{xy(2x - y)}`

`= \frac{(y - 2x)(y + 2x)}{xy(2x - y)}`

`= \frac{-(2x - y)(y + 2x)}{xy(2x - y)}`

`= -\frac{2x + y}{xy}`

`d) \frac{x}{x^2 + xy} + \frac{x - 3y}{y^2 - x^2} + \frac{x}{xy - x^2}`

`= \frac{x}{x(x + y)} + \frac{x - 3y}{(y - x)(y + x)} + \frac{x}{x(y - x)}`

`= \frac{x(y - x) + x(x - 3y) + x(x + y)}{x(x + y)(y - x)}`

`= \frac{xy - x^2 + x^2 - 3xy + x^2 + xy}{x(x + y)(y - x)}`

`= \frac{x^2 - xy}{x(x + y)(y - x)}`

`= \frac{x(x - y)}{-x(x + y)(x - y)}`

`= -\frac{1}{x + y}`

`e) \frac{x^2 + 4}{x - 2} + \frac{4x}{2 - x}`

`= \frac{x^2 + 4}{x - 2} - \frac{4x}{x - 2}`

`= \frac{x^2 - 4x + 4}{x - 2}`

`= \frac{(x - 2)^2}{x - 2}`

`= x - 2 `