Suppose you have a function [itex]y(x)[/itex].
What are then the following functions?
[itex]y(x) + a[/itex]
[itex]y(x) - a[/itex]
[itex]y(x + a)[/itex]
[itex]y(x - a)[/itex]
If you don't see it, try filling in something simple like a linear graph (e.g. [itex]y(x) = x[/itex]) and plotting the functions (two points will do for these), then try to find the argument and check that it applies to any function.
Okay so the parabola looks exactly the same execpt the x values are shifted by 5. If the original parabola was y= x2- 15, (so that y(5)= 52-15= 10) and changing x gives something of the form y= ( )2- 15, what would you put in the parentheses (i.e. changing x) so that y(10)= 15? Hint: if y= (x-5)2- 15, then y(10)= 52- 15= 10.
Now apply that idea, along with CompuChip's initial respons to your problem.