Answer:
y= 7^-t
Step-by-step explanation:
Equation for exponential decay:
An equation represents exponential decay if a term between 0 and 1 is elevated to the independent variable.
In this question:
First option 4 is elevated, so not exponential decay.
Second option:

, thus, the second option represents exponential decay.
Percentages are used to show the fraction of a thing. For example, if 5 students out of 20 like math, the percentage is 5/20 x 100= 25%
<h3>What is a Percentage?</h3>
This refers to the number of ratios that is described as a fraction of 100 and is denoted by the sign %.
Hence, we can see that although your question is incomplete, I gave you a general overview of percentages for a better understanding of the concept.
Read more about percentages here:
brainly.com/question/16865197
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A. 6c
B. -5c
C. -0.7c
D. 2c
Just a few you could use.
![\dfrac\partial{\partial y}\left[e^{2y}-y\cos xy\right]=2e^{2y}-\cos xy+xy\sin xy](https://tex.z-dn.net/?f=%5Cdfrac%5Cpartial%7B%5Cpartial%20y%7D%5Cleft%5Be%5E%7B2y%7D-y%5Ccos%20xy%5Cright%5D%3D2e%5E%7B2y%7D-%5Ccos%20xy%2Bxy%5Csin%20xy)
![\dfrac\partial{\partial x}\left[2xe^{2y}-y\cos xy+2y\right]=2e^{2y}+y\sin xy](https://tex.z-dn.net/?f=%5Cdfrac%5Cpartial%7B%5Cpartial%20x%7D%5Cleft%5B2xe%5E%7B2y%7D-y%5Ccos%20xy%2B2y%5Cright%5D%3D2e%5E%7B2y%7D%2By%5Csin%20xy)
The partial derivatives are not equal, so the equation is not exact.