Secant line question?

Question

For the function f(x) = -x^2, find the slop of the secant line between the points where x = -2 and -4.

a) -20
b) -6
c) -12
d) 6

Answer 1

value of f(-2) = -4 (-2,-4)
value of f(-4) = -16 (-4,-16)

slope = (y2 - y1) / (x2 - x1)
y's = -16 - (-4) = -12
x's = -4 - (-2) = -2

-12/-2 = 6

answer is D

Answer 2

The secant line intersects the parabola at two points.

y = -x² = -(-2)² = -4

y = -x² = -(-4)² = -16

So the two points are (-2,-4) and (-4,-16).

The slope m is calculated as:

m = ∆y / ∆x = (-4 - (-16)) / (-2 - (-4))

m = (-4 + 16) / (-2 + 4) = 12 / 2 = 6

The answer is d.