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?

Answer 1

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

Answer 2

yeah that's not the answer but thx :P

Answer 3

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

Answer 4

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

Answer 5

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

Answer 6

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

Answer 7

okay never mind i got it!

Answer 8

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

Answer 9

thank you!

Answer 10

youre welcome