When x> is at 1, f' (x) > e1-e = 0-e = 0, so f(x) is in x >; 1 interval monotonically increases.
And f( 1)=e-e =0, so when x >;; At 1, f (x) >: F( 1)=0 is E X >;; Ex-husband; Ex-wife; Ex-boyfriend; Ex-girlfriend