To find the slope of a line that passes through two points $(x_1, y_1)$ and $(x_2, y_2)$, we use the slope formula:

$m = \frac{y_2 - y_1}{x_2 - x_1}$

Given the points $(9, 1)$ and $(10, -1)$:

• $x_1 = 9$, $y_1 = 1$
• $x_2 = 10$, $y_2 = -1$

Substitute these values into the slope formula:

$m = \frac{-1 - 1}{10 - 9} = \frac{-2}{1} = -2$

Thus, the slope of the line is $-2$.

Would you like more details or further explanation?

Here are 5 related questions for practice:

1. What is the slope of the line passing through $(2, 5)$ and $(6, 3)$?
2. If a line has a slope of $-3$ and passes through the point $(1, 2)$, what is its equation?
3. How would you determine if two lines are parallel based on their slopes?
4. Find the slope of a vertical line passing through $(4, 2)$.
5. What is the slope of a horizontal line passing through $(5, 7)$?

Tip: A line is horizontal when its slope is 0, and it's vertical when the slope is undefined.