A certain quantity decays exponentially over time. The initial quantity at t = 0 is 1,000. The quantity decays at a rate of 2%. What is the quantity at t = 4?
A. 0.00016
B. 1.6000
C. 903.9208
D. 922.3682

D: 922.3682

Step-by-step explanation:

First you take 1000 and subtract 20 from it.( 2% of 1000 = 1000x0.02x2=20).

You could do this on a calculator by entering 1000 and then subtracting 2% by clicking minus then, 2 then percent, then equals. you get 980. do the same to 980. (click minus, then 2, then percent, then equals). you get 960.4. do the same to 960.4. you get 941.192. do the same one more time since it says t=4  and you get 922.36816 which rounded to the nearest ten-thousandths is 922.3682.

hope this helped!

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this

step-by-step explanation: