In question 1, D is missing, but I assume it's where the line from C meets AB.
So, look at :
Now use :
, since is impossible in this case.
I think you may have written down some of the other questions wrong as well. But here are a few pointers.
2 Note that , and then express all the lengths in terms of . So:
Substitute all these values into , and divide through by .
I think you have written 2(b) wrong. It doesn't work out as you have written it.
3 Express and in terms of . Again, I think you haven't written the result correctly. I think it should be
The result then factorises:
4 Should there be some more information in the diagram? Have you written the result correctly?