### Home > CALC > Chapter 3 > Lesson 3.3.1 > Problem 3-88

3-88.

Given

*f*(*x*) below, find*f*′(*x*). Homework Help ✎*f*(*x*) = −*x**f*(*x*) = 0*f*(*x*) = 9*x*+ sin*x*

You should know by now that a derivative is a slope function. Notice that this is a linear equation, and linear equations have constant slopes.

SImilarly, this is a horizontal line. What is the slope of a horizontal line? That will also be the derivative.

Recall that the derivative of sin(*x*) is cos(*x*).