Multiply the numerator and denominator by the conjugate of the denominator to find
2
+
i
1
−
i
=
1
2
+
3
2
i
Explanation:
The conjugate of a complex number
a
+
b
i
is
a
−
b
i
. The product of a complex number and its conjugate is a real number. We will use this fact to eliminate the complex number from the denominator of the given expression.
2
+
i
1
−
i
=
(
2
+
i
)
(
1
+
i
)
(
1
−
i
)
(
1
+
i
)
=
2
+
2
i
+
i
−
1
1
+
i
−
i
+
1
=
1
+
3
i
2
=
1
2
+
3
2
i
How do I simplify this?
-5+i/2i
I have been having trouble with the imaginary number concept and would like some help with this question. Thanks so much!
4 answers
sorry the numbers got messed up
All good! Thank you so much! You are very helpful!!
since i^2 = -1,
1/i = -i
so (-5+i)/(2i) = (-5+i)(-i/2) = 1/2 + 5/2 i
or, using the conjugate,
(-5+i)/(0+2i) = (-5+i)(0-2i)/(0^2+2^2) = (-5+i)(-2i)/4 = 1/2 + 5/2 i
1/i = -i
so (-5+i)/(2i) = (-5+i)(-i/2) = 1/2 + 5/2 i
or, using the conjugate,
(-5+i)/(0+2i) = (-5+i)(0-2i)/(0^2+2^2) = (-5+i)(-2i)/4 = 1/2 + 5/2 i