Question

Find the product of 5+i and 4-i​

Answer 1

21 - i

Explanation:

( 5+i ) * ( 4-i ) = 5 * ( 4-i ) + i *( 4-i )

= 5*4 - 5*i + i*4 - i*i

= 20 - 5i + 4i - i²

= 20 - 5i +4i - (-1) { i² = -1 }

= 20 - 5i +4i + 1

= 21 - i