(
1
+
2
i
)
(
1
+
i
)
=
1
+
i
+
2
i
+
2
i
2
=
−
1
+
3
i
(
1
+
2
i
)
(
1
+
i
)
=
1
+
i
+
2
i
+
2
i
2
=
−
1
+
3
i
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