Which sequence of steps is a correct derivation of the difference quotient for [tex]\( f(x) = 3 - \log x \)[/tex] ?

[tex]\[
\begin{array}{l}
\frac{f(x+h) - f(x)}{h} \\
=\frac{(3 - \log (x + h)) - (3 - \log x)}{h} \\
=\frac{3 - \log (x + h) - 3 + \log x}{h} \\
=\frac{-\log (x + h) + \log x}{h}, \quad h \neq 0
\end{array}
\][/tex]

[tex]\[
\begin{array}{l}
\frac{f(x+h) - f(x)}{h} \\
=\frac{(3 - \log (x + h)) - (3 - \log x)}{h} \\
=\frac{3 - \log (x + h) - 3 - \log x}{h} \\
=\frac{-\log (x + h) - \log x}{h}, \quad h = 0
\end{array}
\][/tex]



Answer :

To determine the correct sequence of steps for deriving the difference quotient for the function [tex]\( f(x) = 3 - \log x \)[/tex], let's follow the step-by-step method.

The difference quotient formula is given by:

[tex]\[ \frac{f(x+h) - f(x)}{h} \][/tex]

Substituting [tex]\( f(x) = 3 - \log x \)[/tex] and [tex]\( f(x+h) = 3 - \log (x+h) \)[/tex] into the difference quotient, we get:

[tex]\[ \frac{(3 - \log (x+h)) - (3 - \log x)}{h} \][/tex]

Next, simplify the expression inside the numerator:

[tex]\[ \frac{3 - \log (x+h) - 3 + \log x}{h} \][/tex]

Combine like terms (the constant 3's cancel each other out):

[tex]\[ \frac{-\log (x+h) + \log x}{h} \][/tex]

Reordering the terms in the numerator gives:

[tex]\[ \frac{\log x - \log (x+h)}{h} \][/tex]

Thus, the correct sequence of steps is as follows:

[tex]\[ \frac{f(x+h)-f(x)}{h} \][/tex]
[tex]\[ = \frac{(3-\log (x+h))-(3-\log x)}{h} \][/tex]
[tex]\[ = \frac{3-\log (x+h)-3+\log x}{h} \][/tex]
[tex]\[ = \frac{-\log (x+h)+\log x}{h} ; \quad h \neq 0 \][/tex]

Therefore, the first sequence of steps is the correct one.