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I may you please help me with the diritives for AP Calculus

I may you please help me with the diritives for AP Calculus-example-1
User Eduardo Montoya
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1 Answer

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12 votes

To find the derivative of a composite function we use the chain rule


f(g(x))^(\prime)=f^(\prime)(g(x))g^(\prime)(x)

Then, we first find the derivatives of f and g. The function f is of the form


\begin{gathered} (d)/(dx)u^a=au^(a-1)(du)/(dx) \\ u=x^2-3 \\ a=(1)/(2) \\ (du)/(dx)=2x \end{gathered}

Then


f^(\prime)(x)=(1)/(2)(x^2-3)^(-1/2)(2x)=\frac{x}{\sqrt[]{x^2-3}}

On the other hand, the derivative of g is very simple


g^(\prime)(x)=4

After doing this, we evaluate f' in g(x), and we have


f^(\prime)(g(x))=\frac{4x-2}{\sqrt[]{(4x-2)^2-3}}

Replacing f'(g(x)) and g'(x) we obtain


f(g(x))^(\prime)=f^(\prime)(g(x))g^(\prime)(x)\text{ = }\frac{4x-2}{\sqrt[]{(4x-2)^2-3}}\cdot4

Finally, we evaluate this expression in x=1


(f\circ g)^(\prime)(1)=4\frac{4(1)-2}{\sqrt[]{(4(1)-2)^2-3}}=4\cdot\frac{2}{\sqrt[]{2^2-3}}=(8)/(1)=8

Then, the answer is 8

User Everth
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