PROBLEM
Find δ such that if ∣x−1∣<δ, then ∣f(x)−1∣<0.2, given f(1)=1, f(1.1)=0.8, f(1.2)=1.2.
STEP 1
Assumptions1. The function f has a known point (1,1).
. The function f intersects the line y=0.8 at x=1.1.
3. The function f intersects the line y=1. at x=1..
4. We need to find a number δ such that if ∣x−1∣<δ then ∣f(x)−1∣<0..
STEP 2
We are given that f(x) intersects the lines y=0.8 and y=1.2 at x=1.1 and x=1.2 respectively. This means that f(1.1)=0.8 and f(1.2)=1.2.
STEP 3
We are looking for a δ such that if ∣x−1∣<δ then ∣f(x)−1∣<0.2. This means that the values of f(x) should lie between 0.8 and 1.2 when x is in the interval (1−δ,1+δ).
STEP 4
Since f(1.1)=0.8 and f(1.2)=1.2, we can see that the values of f(x) lie between 0.8 and 1.2 when x is in the interval (1.1,1.2).
STEP 5
Therefore, we can choose δ such that (1−δ,1+δ) is a subset of the interval (1.1,1.2).
SOLUTION
The distance between 1 and 1.1 is 0.1 and the distance between 1 and 1.2 is 0.2. Therefore, we choose δ to be the smaller of these two distances, which is 0.1.
So, δ=0.1.
With this choice of δ, if ∣x−1∣<δ then ∣f(x)−1∣<0.2.
Start understanding anything
Get started now for free.