### Home > CALC > Chapter 10 > Lesson 10.3.1 > Problem10-120

10-120.

A function that satisfies the differential equation $f^\prime(x) + f(x) = 0$ is:

1. $f(x) =\operatorname{sin} x$

1. $f(x) =\operatorname{cos} x$

1. $f(x) = e^x$

1. $f(x) = e^{−x}$

1. $f(x) =\operatorname{ln} x$

$\text{Integrate: }\ln|y|=-x+C$
$y=Ce^{-x}$