In advanced mathematics, where you zoom in and out, that derivative will become larger if you add an absolute value? What's going on here?
|a|≥a (the absolute value of any real number is greater than or equal to itself. )
When a≥0, | a | = a
When a<0, | a | =-a>；; a
So |a|≥a
Similarly |f'(x)|≥f'(x)
f(x)-f'(x)≥f(x)-|f'(x)|
e^(-x)[f(x)-f'(x)]≥e^(-x)[f(x)-|f'(x)|]
I hope it helps you.