A simple differentiating problem

This is edexcel C4 differentiating question that i need help in. Thanks in advance!

Q: Find an expression in terms of x and y for $\frac{dy}{dx}$, given that $(x-y)^4 = x+y+5$

My attempt: $\frac{-4dy}{dx}(x-y)^3 = 1+\frac{dy}{dx}$

=> $\frac{dy}{dx}+\frac{4dy}{dx}(x-y)^3 = -1$

Hence $\frac{dy}{dx} = \frac{-1}{1+4(x-y)^3}$

But according to the mark scheme of the textbook, the answer is $\frac{4(x-y)^3-1}{1+4(x-y)^3}$

Once again, help is appreciated!