Write the Word or Phrase That Best Completes Each Statement $\mathrm { f } ( \mathrm { x } ) = 2 \mathrm { x } - 2$

Write the word or phrase that best completes each statement or answers the question.
- $\mathrm { f } ( \mathrm { x } ) = 2 \mathrm { x } - 2$ is defined on the interval $[ 1,5 ]$ . In (a) and (b), approximate the area under $\mathrm { f }$ as follows:
(a) Partition $[ 1,5 ]$ into four subintervals of equal length and choose $u$ as the left endpoint of each subinterval.
(b) Partition $[ 1,5 ]$ into four subintervals of equal length and choose $u$ as the right endpoint of each subinterval.
(c) What is the actual area A?