Answer: x³ + x² + x + C.
- A x³ + x² + x + C
- B 6x + 2 + C
- C 3x + 2 + C
- D x³ + x + C
Correct answer: A. x³ + x² + x + C
Explanation: Integrate each term: x³ + x² + x + C.
The exact area under the curve from a to b (shaded) is approximated by a few rectangles, the Riemann sum idea behind the definite integral.