Answer: B
Step-by-step explanation:
It's the only one that's correct.
The equation will be of the form:

where A is the amount after t hours, and r is the decay constant.
To find the value of r, we plug the given values into the equation, giving:

Rearranging and taking natural logs of both sides, we get:


The required model is:
Answer:
C
Step-by-step explanation:
the equation of a line in slope- intercept form is
y = mx + c ( m is the slope and c the y-intercept )
to calculate m use the gradient formula
m = ( y₂ - y₁ ) / ( x₂ - x₁ )
with (x₁, y₁ ) = (0, - 2) and (x₂, y₂ ) = (4, - 1) ← 2 points on the line
m =
= 
note that the line crosses the y-axis at (0, - 2) ⇒ c = - 2
y =
x - 2 ← equation of line
Start point A = (-4, 1) over y, A = (4,1) over x, A = (4, -1) rotated 180 degrees.