Answer
The symmetric difference quotient is the slope of the secant line connecting the points $(a − h, f (a − h))$ and $(a + h, f (a + h))$ on the graph of $f$.
Work Step by Step
The symmetric difference quotient
$$
\frac{f(a+h)-f(a-h)}{2 h}
$$
is the slope of the secant line connecting the points $(a − h, f (a − h))$ and $(a + h, f (a + h))$ on the graph of $f$.
The difference in the function values is divided by the difference in the $x-$values.
