Question

CALCULUS: Determine which function is a solution to the differential equation y ' − y = 0.

Answer 1

C: none of these are solutions to the given equation.

• If y(x) = e², then y is constant and y' = 0. Then y' - y = -e² ≠ 0.

• If y(x) = x, then y' = 1, but y' - y = 1 - x ≠ 0.

The actual solution is easy to find, since this equation is separable.

y' - y = 0

dy/dx = y

dy/y = dx

∫ dy/y = ∫ dx

ln|y| = x + C

y = exp(x + C )

y = C exp(x) = C eˣ