Which of the following is NOT a valid definition of a derivative? (1 point) Responses f′(a)=limx→af(x)−f(a)x−a f ' ( a ) = lim x → a f ( x ) − f ( a ) x − a f′(a)=limh→0f(a+h)−f(a−h)2h f ' ( a ) = lim h → 0 f ( a + h ) − f ( a − h ) 2 h f′(x)=limh→0f(x+h)−f(h)h f ' ( x ) = lim h → 0 f ( x + h ) − f ( h ) h f′(x)=limh→0f(x+h)−f(x)h f ' ( x ) = lim h → 0 f ( x + h ) − f ( x ) h f′(x)=limh→0f(x+h)−f(x−h)2h
