Final answer:
The slope of a line perpendicular to the line 4x - 8y = 64 is -2, because it is the negative reciprocal of the original line's slope, which is 1/2.
Step-by-step explanation:
To determine the slope of a line that is perpendicular to the given line 4x - 8y = 64, we first need to find the slope of the original line. We can rewrite the equation in slope-intercept form (y = mx + b), where m represents the slope and b the y-intercept. By rearranging the equation, we get 8y = 4x - 64, and then y = (1/2)x - 8. The slope of the original line is therefore 1/2. A line that is perpendicular to this one will have a slope that is the negative reciprocal of 1/2, which is -2.
Therefore, the correct answer is: b. Slope is -2 because it's the negative reciprocal of the original line's slope.