how do i write the expression in the standard form a+b i? (9-5 i)(3 + i )

Question

How do I write the expression in the standard form a + b I.  ( 9-5 i) (3 + i)  ?

Answer 1

(9-5i)(3+i) = 27 +9i -15i -5i^2 = 27 -6i -5*(-1) = 27+5-6i= 32-6i

 

Answer 2

 

before i start, here are some notes for "i"

 

i = √(-1)

i^2 = -1

i^3 = -√(-1)

i^4 = 1

 

foil method for ( 9-5 i) (3 + i)

 

27+9i -15i -5i^2 = 27 - 6i - 5(-1) = 27 -6i +5 = 32 -6i

 

answer is 32 -6i