Q. Given f(x)=2x−3, find f′(−2) using the definition of a derivative.
Define derivative limit: To find f′(−2), we need to use the definition of the derivative, which is the limit of the average rate of change as the change in x approaches 0.
Substitute values: The definition of the derivative is f′(x)=limh→0hf(x+h)−f(x).
Calculate f(−2+h): Substitute x with −2 and f(x) with 2x−3 into the definition: f′(−2)=limh→0hf(−2+h)−f(−2).
Substitute into limit: Calculate f(−2): f(−2)=2(−2)−3=−4−3=−7.
Simplify expression: Substitute f(−2+h) and f(−2) into the limit: f′(−2)=limh→0h(−4+2h−3)−(−7).
Further simplify: Simplify the expression inside the limit: f′(−2)=limh→0h[2h−4+3+7].
Divide by h: Further simplify the expression: f′(−2)=limh→0h2h+6.
Identify mistake: Divide each term by h: f′(−2)=limh→0[2+h6].
Identify mistake: Divide each term by h: f′($−2) = \lim_{h\to0} [2 + \frac{6}{h}]\).As h approaches 0, the term h6 approaches infinity, which is incorrect since we expect a finite number for the derivative. There's a mistake in the previous step.
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