what is the limit x-0 - for f prime (0) when f(x) = -2x^2+4x for x

Question

what is the limit x->0 - for f prime (0)
when f(x) = -2x^2+4x for x<0
show all work please

zepdrix · Answer

I'm confused by the wording. So we want to find this?
$$\lim_{x \rightarrow 0^-}f'(0)$$

zepdrix · Answer

Do you feel comfortable finding f'(x)? :)

anonymous · Answer

yes, sorry if that was confusing

anonymous · Answer

I know that f'(x) Does not exist, but I have to still show my work for finding the limits as x->0 - and x->0+. My answer for x->0- is wrong and I dont know why so i'm hoping to see how someone else does it

zepdrix · Answer

$$f'(x)=-4x+4$$$$\lim_{x \rightarrow 0^-}f'(x)=-4(0)+4=4$$
Does that look right? :o

anonymous · Answer

according to my webwork, its still not right..

zepdrix · Answer

Hmmmmmmmmm

campbell_st · Answer

well you have to be careful and look at the initial conditions, which say x< 0 

so you can't substitute x = 0 and evaluate to find the limit...

zepdrix · Answer

Oh interesting :O