Question

Please help me with this problem

Answer 1

`\begin{gathered} (c^2-d^2)/(d^2+cd-2c^2) \\ (\left(c+d\right)\left(c-d\right))/(d^2+cd-2c^2) \\ (\left(c+d\right)\left(c-d\right))/(\left(2c+d\right)\left(-c+d\right)) \\ -(c+d)/(2c+d) \end{gathered}`
`(-c-d)/(d+2c)`

the third one