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A-level Mathematics/MEI/FP1/Complex Numbers/basic operations solutions
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A-level Mathematics
|
MEI
|
FP1
|
Complex Numbers
1.
5
j
+
3
j
=
(
5
+
3
)
j
=
8
(
j
)
=
8
j
{\displaystyle 5j+3j=(5+3)j=8(j)=8j}
2.
7
(
3
j
)
=
(
7
)
(
3
)
(
j
)
=
21
(
j
)
=
21
j
{\displaystyle 7(3j)=(7)(3)(j)=21(j)=21j}
3.
(
9
+
2
j
)
(
1
−
j
)
+
3
−
2
j
=
9
−
2
j
2
−
2
j
−
9
j
+
3
−
2
j
=
9
−
11
j
−
(
2
)
(
−
1
)
+
3
−
2
j
=
9
+
2
+
3
−
11
j
−
2
j
=
14
−
13
j
{\displaystyle (9+2j)(1-j)+3-2j=9-2j^{2}-2j-9j+3-2j=9-11j-(2)(-1)+3-2j=9+2+3-11j-2j=14-13j}
4.
(
21
+
7
j
)
÷
7
=
21
÷
7
+
7
j
÷
7
=
3
+
j
{\displaystyle (21+7j)\div 7=21\div 7+7j\div 7=3+j}
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