Q. Find the derivative of the following function.y=log9(−5x4−x3)Answer: y′=
Identify function and base: Identify the function and the base of the logarithm.We are given the function y=log9(−5x4−x3). The base of the logarithm is 9.
Apply chain rule: Apply the chain rule for differentiation.The chain rule states that the derivative of a composite function is the derivative of the outer function evaluated at the inner function times the derivative of the inner function.In this case, the outer function is log9(u) and the inner function is u=−5x4−x3.
Differentiate outer function: Differentiate the outer function with respect to the inner function.The derivative of log9(u) with respect to u is u⋅ln(9)1, where ln is the natural logarithm.
Differentiate inner function: Differentiate the inner function with respect to x. The inner function is u=−5x4−x3. Using the power rule, the derivative is dxdu=−20x3−3x2.
Apply chain rule multiplication: Apply the chain rule by multiplying the derivatives from Step 3 and Step 4.The derivative of y with respect to x is dxdy=(−5x4−x3⋅ln(9))1⋅(−20x3−3x2).
Simplify expression: Simplify the expression.We can factor out x2 from the numerator and combine the terms to get the final derivative.dxdy=(−5x4−x3)⋅ln(9)−20x3−3x2dxdy=x3(−5x−1)⋅ln(9)x2(−20x−3)dxdy=x(−5x−1)⋅ln(9)−20x−3
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