# How do you multiply -4b(1-9b-2b^2)?

May 11, 2018

$8 {b}^{3} + 36 {b}^{2} - 4 b$

#### Explanation:

Just Distribute $- 4 b$ and multiply with each term.
$- 4 b \left(1 - 9 b - 2 {b}^{2}\right) = \left(- 4 b\right) \left(1\right) - \left(- 4 b\right) \left(9 b\right) - \left(- 4 b\right) \left(2 {b}^{2}\right)$

Watch out for Sign Changes, if any.
$= - 4 b + 36 {b}^{2} + 8 {b}^{3}$

Re-order from highest power to lowest:
$= 8 {b}^{3} + 36 {b}^{2} - 4 b$