Question

Which one of the following does not find the value of f ′(5) for f(x) = 3x^2 - 2x - 4?

Answer 1

so.. .any ideas?

recall the definition of a limit \(\bf \lim\limits_{h\to0}\ f(x)\iff \cfrac{f(x+h)-f(x)}{h}\)

Answer 2

not really but I was told to plug in 5 for x and i got 61

Answer 3

well... the given choices do not rely on a scalar value, that is, one constant

so... you'd have to use the definition of a limit equation and plug that in
then change the x to a 5 :)

Answer 4

I'm not really sure how to go about that

Answer 5

am I using the equation you wrote out above?

Answer 6

ok.... so...

if we had say f(x)=2x+3
what would be f(7)?

Answer 7

do I plug in 7 for x and get 17?

Answer 8

@jdoe0001 ?

Answer 9

well, what you're being asked is
which one of those 3 choices, is not good to get the derivative at 5

so... first off, you'd want to put the original equation, in derivative terms

the 1st and last choices, are using the "definition of a limit" form, the one I posted it
which your book should have, and you should have covered already

the middle choice, is using a different form, just a straight up limit approach

Answer 10

f(x) = 3x^2 - 2x - 4
derivative f'(x)= 6x-2

Answer 11

i am lost
it says "all of these find it"

Answer 12

last one looks like it has a plus sign where there should be a minus sign though

Answer 13

yeah that first plus sign in the numerator of the third one should be a minus