Apply Power Rule: To find the derivative of the function f(x)=x21, we need to apply the power rule for derivatives. The power rule states that the derivative of xn with respect to x is n⋅x(n−1). In this case, we can rewrite the function as f(x)=x−2 and then apply the power rule.
Calculate Derivative: Applying the power rule, we get f′(x)=−2⋅x(−2−1)=−2⋅x−3. This simplifies the derivative of the function to f′(x)=−x32.
Substitute x=5: Now we need to evaluate the derivative at x=5. We substitute x with 5 in the derivative function f′(x)=−x32 to get f′(5)=−532.
Evaluate f′(5): Calculating the value of f′(5), we have f′(5)=−(53)2=−1252.
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