Section 2.2-Work with difference quotient
One difficulty of working with the definition of the derivative is working through the algebra of the difference quotient (slope of the secant line). These problems allow practice working with a difference quotient, except using y rather than h which is how the difference quotient is typically presented.
See
https://www.khanacademy.org/math/calculus/differential-calculus/secant-line-slope-tangent/v/slope-of-a-line-secant-to-a-curve
for videos about why we will need this topic.