Answer:
43 + 7i
Step-by-step explanation:
Given: (1 + 5i)(3 - 8i)
To find: Multiplication and simplification
Solution:
i=[tex]\sqrt{-1}[/tex],
Now, we simply open the brackets as follows:
(1 + 5i)(3 - 8i)
1(3 - 8i) + 5i (3 - 8i)
3 - 8i + 15i - 40[tex]i^{2}[/tex]
3 + 7i - 40[tex]i^{2}[/tex] - (i)
[tex]i^{2}[/tex] = i * i
[tex]i^{2}[/tex] = [tex]\sqrt{-1}[/tex] * [tex]\sqrt{-1}[/tex]
[tex]i^{2}[/tex] = -1
Now, put [tex]i^{2}[/tex] = -1 into the equation (i)
we get
⇒ 3 + 7i -40(-1)
⇒ 3 + 7i + 40
⇒ 43 + 7i
∴ Final Answer : 43 + 7i
[tex]\qquad\qquad\huge\underline{{\sf Answer}}[/tex]
Here we go ~
what we need to know here is that :
[tex]\qquad \sf \dashrightarrow \:i \cdot i = - 1[/tex]
Now, let's proceed accordingly ~
[tex]\qquad \sf \dashrightarrow \:(1 + 5i) \cdot(3 - 8i)[/tex]
[tex]\qquad \sf \dashrightarrow \:(1 \cdot3) - (1 \sdot8i) + (5i \cdot3) - (5i \cdot8i)[/tex]
[tex]\qquad \sf \dashrightarrow \:3 - 8i + 15i - ( - 1)(40)[/tex]
[tex]\qquad \sf \dashrightarrow \:3 + 7i - ( - 40)[/tex]
[tex]\qquad \sf \dashrightarrow \:3 + 40 + 7i[/tex]
[tex]\qquad \sf \dashrightarrow \:43 + 7i[/tex]
