Answer:
B. In the multiplication of the imaginary parts, the student forgot to square the i.
C. The student has only multiplied the real parts and the imaginary parts.
Step-by-step explanation:
Before we figure out the student mistake, let us find the product of the complex numbers ourselves first.
(4+5i) (3-2i)
open the parenthesis
= 4(3)-4(2i)+3(5i)+5i(-2i)
= 12-8i+15i-10i²
Note that in complex number, i² = -1, hence the expression will become;
= 12-8i+15i-10(-1)
= 12-8i+15i+10
collect like terms by separating the real from imaginary part
= 12+10-8i+15i
= 22+7i
From the students answer i.e 12-10i, it can be concluded that;
In the multiplication of the imaginary parts, the student forgot to square the i and the student has only multiplied the real parts and the imaginary parts 4 and 3 to get 12
