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What is the value of 
(d)/(dx)(x^(-3)) at 
x=3 ?

What is the value of ddx(x3) \frac{d}{d x}\left(x^{-3}\right) at x=3 x=3 ?

Full solution

Q. What is the value of ddx(x3) \frac{d}{d x}\left(x^{-3}\right) at x=3 x=3 ?
  1. Identify Function & Operation: Identify the function and the operation needed.\newlineWe need to find the derivative of the function f(x)=x3f(x) = x^{-3} with respect to xx and then evaluate this derivative at x=3x=3.
  2. Apply Power Rule: Apply the power rule for differentiation.\newlineThe power rule states that the derivative of xnx^n with respect to xx is nx(n1)n*x^{(n-1)}. Applying this rule to our function, we get:\newlinef(x)=ddx(x3)=3x(31)=3x4.f'(x) = \frac{d}{dx}(x^{-3}) = -3*x^{(-3-1)} = -3*x^{-4}.
  3. Simplify Derivative Expression: Simplify the expression for the derivative. f(x)=3x4f'(x) = -3x^{-4} can be rewritten as f(x)=3x4f'(x) = -\frac{3}{x^4} for easier evaluation.
  4. Evaluate at x=3x=3: Evaluate the derivative at x=3x=3.\newlineSubstitute xx with 33 in the expression for f(x)f'(x):\newlinef(3)=334=381f'(3) = -\frac{3}{3^4} = -\frac{3}{81}.
  5. Simplify Result: Simplify the result.\newline381-\frac{3}{81} simplifies to 127-\frac{1}{27}.

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