Let f be a differentiable function such that f(3)=15, f(6)=3, f ' (3)= -8, and f ' (6)= -2. The function g is differentiable and g(x)= f inverse (x) for all x. What is the value of g '(3)
A: -1/2B: -1/8C: 1/6D: 1/3E: Value cannot be determined

Respuesta :

Answer:

A. [tex]g'(3)=-\frac{1}{2}[/tex]

Step-by-step explanation:

We have been given that f be a differentiable function such that[tex]f(3)=15[/tex], [tex]f(6)=3[/tex], [tex]f'(3)= -8[/tex], and [tex]f'(6)= -2[/tex]. The function g is differentiable and [tex]g(x)= f^{-1} (x)[/tex] for all x.

We know that when one function is inverse of other function, so:

[tex]g(f(x))=x[/tex]

Upon taking derivative of both sides of our equation, we will get:

[tex]g'(f(x))*f'(x) =1[/tex]

[tex]g'(f(x))=\frac{1}{f'(x)}[/tex]

Plugging [tex]x=6[/tex] into our equation, we will get:

[tex]g'(f(6))=\frac{1}{f'(6)}[/tex]

Since [tex]g(x)= f^{-1} (x)[/tex], then [tex]g'(f(6))=g'(3)[/tex].

[tex]g'(3)=\frac{1}{f'(6)}[/tex]

Since we have been given that [tex]f'(6)= -2[/tex], so we will get:

[tex]g'(3)=\frac{1}{-2}[/tex]

[tex]g'(3)=-\frac{1}{2}[/tex]

Therefore, [tex]g'(3)=-\frac{1}{2}[/tex] and option A is the correct choice.