## University Calculus: Early Transcendentals (3rd Edition)

$9b^{3}$
We know that $\int^{b}_{0}x^{2}dx= \frac{b^{3}}{3}$ Then $\int^{3b}_{0}x^{2}dx= \frac{(3b)^{3}}{3}=\frac{27b^{3}}{3}=9b^{3}$