# How do you multiply 3y ^ { 2} + 6y + 5 and y - 9 using the vertical format?

Mar 15, 2017

$3 {y}^{3} - 21 {y}^{2} - 49 y - 45$

#### Explanation:

Multiplying in vertical format is the same as long multiplication with numbers:

$\text{ } 3 {y}^{2} + 6 y + 5$
ul(xx" "color(blue)(y)color(red)( -9)" "larr muliply each term by the top row
color(blue)(3y^3+6y^2+5y
ul(" "color(red)(-27y^2-54y-45))" "larr like terms under each other
$\underline{3 {y}^{3} - 21 {y}^{2} - 49 y - 45} \text{ } \leftarrow$add like terms