Hello TweetyYour working is perfect up to here. Good job!

What you need to realise now is that the tangent at effectively cuts the curve intwo coincident pointswhere .

So will be arepeated rootof your final equation, which is more simply written as:

In other words , or , is a factor of the LHS of:

So we get:(Check it out: multiply out the brackets and you get .)

So the other value of is ...?

I'm sure you can take it from here.

Grandad