Question

Multiply (in horizontal and vertical arrangement):

(4) (a + b) × (b + d)

Answer 1

(a + b) × (b + d)
Horizontal arrangement:
= (a + b) × b + (a + b) × d
= a × b + b × b + a × d + b × d
= ab + b² + ad + bd
Vertical arrangement:
$\begin{array}{c}\begin{array}{ccccccc}& & & & a& +& b\end{array}\\ \begin{array}{ccccccc}& & & \times & b& +& d\end{array}\\ \underline{\overline{\begin{array}{ccccccc}& & & & ad& +& bd\end{array}}}\\ \begin{array}{ccccccc}+ab& +& b^2& & & & \end{array}\\ \underline{\overline{\begin{array}{ccccccc}ab& +& b^2& +& ad& +& bd\end{array}}}\end{array}$