How To Solve Integral of e? And solve velocity?

1) int(1/(1-e^(-x)))

**My attempt:**

ln |1-e^(-x)| + c

**Answer:**

ln |e^x - 1| + c

2) Solve the differential equation:

(e^(x-y))dy=-dx

**My Attempt:**

-1/(e^(x-y))=dy/dx

**Answer:**

0 = e^(-y) + e^(-x) + c

3) a(t) = -32 ft/s as the acceleration due to gravity. An object is vertically thrown downward from the top of the 480 foot building with an initial velocity of 64 ft/s. With what velocity does the object hit the ground?

**My Attempt:**

int(-32) = -32x + c

v = -32x + 480?

**Answer:**

v = -186.56 ft/sec