Suppose that [tex]f(9)=-6, f^{\prime}(9)=3, g(9)=-8[/tex], and [tex]g^{\prime}(9)=7[/tex].

Find the value of [tex]\left(\frac{f}{g}\right)^{\prime}(9)[/tex].



Answer :

To find the value of [tex]\(\left( \frac{f}{g} \right)'(9)\)[/tex], we will use the quotient rule for differentiation. The quotient rule states that if you have two differentiable functions [tex]\(f(x)\)[/tex] and [tex]\(g(x)\)[/tex], then the derivative of their quotient [tex]\(\frac{f(x)}{g(x)}\)[/tex] is given by:

[tex]\[ \left( \frac{f}{g} \right)' = \frac{f'g - fg'}{g^2} \][/tex]

We are given the following values:
- [tex]\(f(9) = -6\)[/tex]
- [tex]\(f'(9) = 3\)[/tex]
- [tex]\(g(9) = -8\)[/tex]
- [tex]\(g'(9) = 7\)[/tex]

We need to find [tex]\(\left( \frac{f}{g} \right)'(9)\)[/tex].

Substitute [tex]\(x = 9\)[/tex] into the quotient rule formula:

[tex]\[ \left( \frac{f}{g} \right)'(9) = \frac{f'(9) \cdot g(9) - f(9) \cdot g'(9)}{g(9)^2} \][/tex]

Substitute the given values into the formula:

[tex]\[ \left( \frac{f}{g} \right)'(9) = \frac{3 \cdot (-8) - (-6) \cdot 7}{(-8)^2} \][/tex]

Calculate the numerator:

[tex]\[ 3 \cdot (-8) = -24 \][/tex]

[tex]\[ -6 \cdot 7 = -42 \][/tex]

[tex]\[ \text{Numerator} = -24 - (-42) = -24 + 42 = 18 \][/tex]

Calculate the denominator:

[tex]\[ (-8)^2 = 64 \][/tex]

Now, combine the numerator and the denominator:

[tex]\[ \left( \frac{f}{g} \right)'(9) = \frac{18}{64} \][/tex]

Simplify the fraction:

[tex]\[ \frac{18}{64} = 0.28125 \][/tex]

Thus, the value of [tex]\(\left( \frac{f}{g} \right)'(9)\)[/tex] is:

[tex]\[ 0.28125 \][/tex]