Q Find the square root of the complex number 5 -12i.
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Answered by
146
Suppose that a+bi is a square root of 5 + 12i.
Then, (a+bi)^2 = (a^2 - b^2) + (2ab)i = 5 + 12i.
Equate real and imaginary parts:
a^2 - b^2 = 5
2ab = 12 ==> b = 6/a.
So, a^2 - (6/a)^2 = 5
==> a^2 - 36/a^2 = 5
==> a^4 -5a^2 - 36 = 0.
==> (a^2 -9)(a^2 + 4) = 0.
Since a must be real, a = 3 or -3.
This gives b = 2 or -2, respectively.
Thus, we have two square roots: 3+2i or -3-2i.
Then, (a+bi)^2 = (a^2 - b^2) + (2ab)i = 5 + 12i.
Equate real and imaginary parts:
a^2 - b^2 = 5
2ab = 12 ==> b = 6/a.
So, a^2 - (6/a)^2 = 5
==> a^2 - 36/a^2 = 5
==> a^4 -5a^2 - 36 = 0.
==> (a^2 -9)(a^2 + 4) = 0.
Since a must be real, a = 3 or -3.
This gives b = 2 or -2, respectively.
Thus, we have two square roots: 3+2i or -3-2i.
Answered by
7
Answer:
dont no
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