the answer is 8 (to first question) - how did you do the working?
GCSE core (grade c - g)
The line with equation y=2x-k passes through the point (4 , 0). Work out the value of k.
Where do i start and what's the simplest way of remembering how to do these?
As for (r^4)^{-2} you just add the powers, so the answer is r^2 (where ^ denotes powers)