lim (x→3) (5^4x−5^12 )/ (3−x)
is equal to the derivative of a function f at a point a (that is, f′(a)).

What is the function f in this case?

Question

lim (x→3) (5^4x−5^12 )/ (3−x)
is equal to the derivative of a function f at a point a (that is, f′(a)). 

What is the function f in this case?

anonymous · Answer

it could most probably be 
$5^{4x}$
but in that case, the denominator would be x-3 and not 3-x

anonymous · Answer

yeah that's not the answer but thx :P

amistre64 · Answer

so its giving you a derivative (the long way) and asking what function its deriving

anonymous · Answer

yes but i don't know  what the original function is

amistre64 · Answer

$$\frac{f(x)-f(a)}{x-a}$$
$$\frac{5^{4x}-5^{4a}}{x-a}$$
$$\frac{5^{4x}-5^{12}}{x-3}$$
$$-\frac{5^{4x}-5^{12}}{3-x}$$
so to keep the parts in place, we are missing a negative arent we

anonymous · Answer

but what is the original function? i got -5^4x but it's only half right!

anonymous · Answer

okay never mind i got it!

amistre64 · Answer

thats the original function, whats the other half of the question?

anonymous · Answer

thank you!

amistre64 · Answer

youre welcome