Math problem. Find interval with solution. Thanks.?

f(x) = (2 - x) eˣ
f'(x) = (1 - x) eˣ
f''(x) = - x eˣ

f(x) is decreasing when f'(x) = (1 - x) eˣ < 0
(1 - x) eˣ < 0
(1 - x) < 0 ...... ( Since eˣ > 0 )
x > 1

The interval is (1,∞)

∴ D. (1,∞)

f"(x)=0
-x eˣ =0
x=0 or eˣ=0 (delete)
-------x<0 x=0 x>0
f'(x) + 0 -

D