Answer: x³ + C.
- A 6x + C
- B x³ + C
- C 3x³ + C
- D 3x + C
Correct answer: B. x³ + C
Explanation: Integral of 3x² = 3 × x³/3 = x³ + 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.