Answer:

Step-by-step explanation:
You have the following differential equation:

This equation can be written as:

where

If the differential equation is exact, it is necessary the following:

Then, you evaluate the partial derivatives:

The partial derivatives are equal, then, the differential equation is exact.
In order to obtain the solution of the equation you first integrate M or N:
(1)
Next, you derive the last equation respect to t:

however, the last derivative must be equal to M. From there you can calculate g(t):
![\frac{\partial F(t,y)}{\partial t}=M=(7y-3t)e^t=7ye^t+g'(t)\\\\g'(t)=-3te^t\\\\g(t)=-3\int te^tdt=-3[te^t-\int e^tdt]=-3[te^t-e^t]](https://tex.z-dn.net/?f=%5Cfrac%7B%5Cpartial%20F%28t%2Cy%29%7D%7B%5Cpartial%20t%7D%3DM%3D%287y-3t%29e%5Et%3D7ye%5Et%2Bg%27%28t%29%5C%5C%5C%5Cg%27%28t%29%3D-3te%5Et%5C%5C%5C%5Cg%28t%29%3D-3%5Cint%20te%5Etdt%3D-3%5Bte%5Et-%5Cint%20e%5Etdt%5D%3D-3%5Bte%5Et-e%5Et%5D)
Hence, by replacing g(t) in the expression (1) for F(t,y) you obtain:

where C is the constant of integration