Q. Find the derivative of the following function.y=log4(7x3−5x2)Answer: y′=
Apply Chain Rule and Logarithmic Differentiation: To find the derivative of the function y=log4(7x3−5x2), we will use the chain rule and the logarithmic differentiation rule. 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. The logarithmic differentiation rule for a logarithm with base a is given by (d/dx)loga(u)=(1/u)⋅(du/dx)⋅(1/log(a)), where u is a function of x.
Express Logarithm with Base 4 in Natural Logarithm: First, we need to express the logarithm with base 4 in terms of the natural logarithm using the change of base formula: loga(u)=ln(a)ln(u). So, y=log4(7x3−5x2) can be rewritten as y=ln(4)ln(7x3−5x2).
Differentiate Quotient Using Quotient Rule: Now, we will differentiate y with respect to x using the quotient rule since y is a quotient of two functions: ln(7x3−5x2) and ln(4). The quotient rule is given by (d/dx)[v(x)/u(x)]=(u(x)∗(dv/dx)−v(x)∗(du/dx))/(u(x))2. However, since ln(4) is a constant, its derivative is 0, and the quotient rule simplifies to just the derivative of the numerator divided by the denominator.
Apply Chain Rule to Differentiate Numerator: We differentiate the numerator ln(7x3−5x2) using the chain rule. The derivative of ln(u) with respect to u is 1/u, so we have (d/dx)ln(7x3−5x2)=1/(7x3−5x2)⋅d/dx(7x3−5x2).
Find Derivative of Inner Function: Next, we find the derivative of the inner function 7x3−5x2 with respect to x. Using the power rule, which states that the derivative of xn with respect to x is n∗x(n−1), we get dxd(7x3−5x2)=21x2−10x.
Combine Results to Find Derivative of y: Now we can combine the results from the previous steps to find the derivative of y. We have y′=7x3−5x21⋅ln(4)21x2−10x.
Simplify Expression for y′: Finally, we simplify the expression for y′ by multiplying the terms. This gives us y′=(7x3−5x2)⋅ln(4)21x2−10x.
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