AP Calculus AB Exam Question:
Let f(x) be a continuous function defined on the closed interval [a, b], where a < b. Determine the limit of the function as x approaches c, where c is a real number within the interval (a, b), using the ϵ-δ definition of a limit.
Consider the function:
f(x)={x2cx+2if x≤cif x>cUsing the ϵ-δ definition of a limit, determine the following limit:
x→climf(x)Step-by-Step Solution:
To find the limit as x approaches c, we will employ the ϵ-δ definition of a limit, which states:
For a given value ϵ>0, there exists a value δ>0 such that if 0<∣x−c∣<δ, then ∣f(x)−L∣<ϵ, where L is the desired limit.
First, let's analyze the behavior of the function on the left and right sides of c.
For x values less than or equal to c:
f(x)=x2For x values greater than c:
f(x)=cx+2Now, let's find the limit of f(x) as x approaches c from the left side.
x→c−limf(x)=x→c−limx2=c2Similarly, let's find the limit of f(x) as x approaches c from the right side.
x→c+limf(x)=x→c+limcx+2=c⋅c+2=c2+2Next, let's combine both limits:
x→climf(x)=x→c−limf(x)=x→c+limf(x)=c2Therefore, the limit of the given function as x approaches c is limx→cf(x)=c2.