The 2 red boxes ... i am getting some different range of the function
if x < -4 + f and 0<=f<1
then shouldn't it be x<-3 ??
and how the < change to <=
the case when f=0 should be separate as for f=0 the third line will become I^2 + I^2 > 25
*the curly bracket are just simple brackets and not fractional part of x