Explanation:
C it translates the whole curve 8 units left.
simply because f(x+8) means that at the position x we get the functional result that should normally happen at the position x+8. but so, it happens 8 units "earlier". therefore, a shift to the left.
f(x-8) would be a shift to the right by 8 units.
f(x) + 8 would be a shift up by 8 units.
f(x) - 8 would be a shift down by 8 units.
oh, and -f(x) would flip it upside-down.