College Algebra
Complex Numbers
Operations with Complex Numbers
Multiplication
Interactive Example 1
If
and
, find
z
1
· z
2
.
z
1
=x
1
+iy
1
x
1
y
1
z
2
=x
2
+iy
2
x
2
y
2
Solution 1
By the definition,
z
1
·
z
2
=
=
Solution 2
By formally manipulating the terms as if they involved only real numbers and by replacing i
2
by -1 when it occurs,
z
1
·
z
2
=
=
=
=
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