# Homework Help: Problem with complex numbers

1. Nov 26, 2006

### Ben_sa

Hello all
I am having this problem with complex number and i don't know exactly how to solve it. Can i get some help with it please:

i) Z1 = 2 + j5, Z2 = 1 – j3 and Z3 = 4 – j determine, in both rectangular and polar form, value of
((Z1 * Z2)/(Z1 + Z2)) + Z3
(Give the final answers to 3 significant figures).

Thanx

2. Nov 26, 2006

### Hootenanny

Staff Emeritus
Welcome to the forums Ben,

Just for future reference there are homework forums, specifically for homework questions. In addition, the rules of the forums state that one must show ones attempt at a question before receiving help...

3. Nov 26, 2006

### Ben_sa

Sorry i forgot about that in the rules
this is my work that i did i hope it is right

((2+j5) * (1-j3))/((2+j5) + (1-j3))

= 2 - j3 +j5 +15/(3+j2)

=((17+2J) * (3-j2))/((3+j2) * (3-j2))

=55 +42j/13

= (4.231 + 3.231j) + (4-j)
= (8.231 + 2.231j)

is that right??
Next time I'll remember to put it in the homework section

4. Nov 26, 2006

### Ben_sa

The previous answer i think was wrong and i think this one is the right one
= 3.769 + j1.538
because there was a mistake in the second line

5. Nov 27, 2006

### Hootenanny

Staff Emeritus