#x# cannot be #<1#, because if #x<1#, there would be a negative under the radical, which cannot exist in the real number system. So #x# can be anywhere from #1# to#prop#.
Since #x# must be at least 1, the value of #y# can range from #sqrt0##=0#, to #sqrt# of any value #>x#, which makes the limit of the range #prop#.