Answer: e 3x /3 + C.
- A 3e<sup>3x</sup> + C
- B e<sup>3x</sup>/3 + C
- C e<sup>3x</sup> + C
- D 3x e<sup>3x</sup> + C
Correct answer: B. e<sup>3x</sup>/3 + C
Explanation: Integral of e<sup>ax</sup> = e<sup>ax</sup>/a + C. Here a=3: e<sup>3x</sup>/3 + 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.