Q. Find the derivative of the following function.y=3−9x4+3x3Answer: y′=
Identify Function Components: Identify the function and its components.We have y=3(−9x4+3x3). This is an exponential function with base 3 and exponent −9x4+3x3.
Apply Chain Rule: Apply the chain rule for derivatives.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 au where a is a constant and u is a function of x, and the inner function is u(x)=−9x4+3x3.
Differentiate Outer Function: Differentiate the outer function with respect to the inner function.The derivative of au with respect to u is au⋅ln(a), where ln(a) is the natural logarithm of a. So, the derivative of 3u with respect to u is 3u⋅ln(3).
Differentiate Inner Function: Differentiate the inner function with respect to x. The inner function is u(x)=−9x4+3x3. Using the power rule, the derivative of −9x4 is −36x3, and the derivative of 3x3 is 9x2. So, the derivative of u(x) with respect to x is u′(x)=−36x3+9x2.
Apply Chain Rule Multiplication: Apply the chain rule by multiplying the derivatives from Step 3 and Step 4.Using the chain rule, the derivative of y with respect to x is y′=(3u⋅ln(3))⋅u′(x), where u=−9x4+3x3 and u′(x)=−36x3+9x2. Substituting u and u′(x) into the equation, we get y′=(3(−9x4+3x3)⋅ln(3))⋅(−36x3+9x2).
Simplify Derivative Expression: Simplify the expression for the derivative. y′=3(−9x4+3x3)⋅ln(3)⋅(−36x3+9x2) can be simplified by factoring out common terms if possible. However, in this case, the expression is already in its simplest form.
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