# How do you multiply #(15+ 13i ) ( 12- 9i )#, assuming #i# is an imaginary number?

##### 1 Answer

#### Explanation:

You multiply them just like real numbers, assuming that

#(15+13i)(12-9i)#

#=15*12+13i*12-15*9i-13i*9i#

#=180+156i-135i+117#

#=297+21i#

You multiply them just like real numbers, assuming that

#(15+13i)(12-9i)#

#=15*12+13i*12-15*9i-13i*9i#

#=180+156i-135i+117#

#=297+21i#