Q. Given f(x)=x+23, find f′(1) using the definition of a derivative.
Given Function: We are given the function f(x)=(x+2)3 and we need to find its derivative at x=1 using the definition of a derivative. The definition of a derivative is:f′(x)=limh→0hf(x+h)−f(x)Let's apply this definition to our function.
Substitute x+h: First, we need to find the expression for f(x+h). This means we will substitute (x+h) for x in the function f(x):f(x+h)=((x+h)+2)3=x+h+23
Plug into Derivative Definition: Now, we will plug f(x+h) and f(x) into the definition of the derivative: f′(x)=h→0lim[(x+h+2)3−(x+2)3]/h
Find Common Denominator: Next, we need to find a common denominator for the terms in the numerator to combine them:The common denominator is (x+h+2)(x+2), so we rewrite the numerator:f′(x)=limh→0[(x+h+2)(x+2)3(x+2)−3(x+h+2)]/h
Simplify Numerator: Now, we simplify the numerator:3(x+2)−3(x+h+2)=3x+6−3x−3h−6=−3hSo the expression becomes:f′(x)=limh→0[((x+h+2)(x+2)⋅h)−3h]
Cancel out h: We can now cancel out the h in the numerator and denominator: f′(x)=limh→0[−((x+h+2)(x+2))3]
Take the Limit: Now we can take the limit as h approaches 0:f′(x)=((x+2)(x+2))−3
Substitute x=1: Finally, we substitute x=1 into the derivative to find f′(1):f′(1)=−((1+2)(1+2))3=−(3×3)3=−93=−31
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