(b) $\int_{0}^{3}{|x^{3} + x^{2} + 3x|dx} = \int_{0}^{3}{(x^{3} + x^{2} + 3x)dx}$ $= \left\lbrack \frac{x^{4}}{4} + \frac{x^{3}}{3} + \frac{3x^{2}}{2} \right\rbrack_{0}^{3}$ $= \frac{81}{4} + \frac{27}{3} + \frac{27}{2} = \frac{171}{4}$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.