Limits question

  • Thread starter kendal12
  • Start date
  • #1
I just started calculus and we are doing limits. I was doing fine on my hmwrk until i came to this problem:

Find lim f(x+∆x) – f(x)/ ∆x
∆x→0

f(x)= x^2 – 4x

I have no idea what the delta means... I know in chem it means "a change in", but I don't know what to do with it here. My book doesn't explain it either. Please help! Thanks
 

Answers and Replies

  • #2
mathmike
208
0
delta x ->0
means as x approaches zero

or in other words the change in the value of x is getting so small that it is almost zero.
 
  • #3
oh so it changes nothing?
 
  • #4
or what am i supposed to do with the delta x value?
 
  • #5
Tide
Science Advisor
Homework Helper
3,089
0
kendal,

My book doesn't explain it either.

I seriously doubt that. For purposes of solving your problem and to get you accustomed to the concept why don't you just replace the [itex]\Delta x[/itex] with something more friendly looking like a? Then you can carry out your algebra and examine what happens when a is made arbitrarily small.
 
  • #6
Trust me. I have read the entire chapter looking for something explaining the delta and there is nothing. Thanks for the tip though.
 
  • #7
ok, so I worked out the problem and got 2x+a... is this correct? For some reason I don't think it is, but I thought I worked it out right...
 
  • #8
Tide
Science Advisor
Homework Helper
3,089
0
You should have gotten [itex]2x - 4 + a[/itex]. Recheck your algebra.
 

Suggested for: Limits question

  • Last Post
Replies
7
Views
522
  • Last Post
Replies
29
Views
497
Replies
6
Views
609
  • Last Post
Replies
3
Views
575
  • Last Post
Replies
29
Views
2K
MHB Limits
  • Last Post
Replies
1
Views
484
  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
13
Views
872
Replies
3
Views
499
  • Last Post
Replies
3
Views
1K
Top