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Problem 11 - Entrance Test
Let i be the imaginary unit. What is the value of ( (1 + i) / (1 - i) )^2024?
Correct: B
First, simplify the base of the expression, (1 + i) / (1 - i):
To simplify, multiply the numerator and denominator by the conjugate of the denominator, which is (1 + i):
(1 + i) / (1 - i) = ( (1 + i) * (1 + i) ) / ( (1 - i) * (1 + i) )
= (1 + 2i + i^2) / (1^2 - i^2)
Since i^2 = -1:
= (1 + 2i - 1) / (1 - (-1))
= (2i) / (1 + 1)
= 2i / 2
= i.
So the expression simplifies to i^2024.
Now, we need to evaluate i^2024. The powers of i cycle with a period of 4:
i^1 = i
i^2 = -1
i^3 = -i
i^4 = 1
i^5 = i, and so on.
To find i^2024, we divide the exponent by 4 and look at the remainder.
2024 / 4 = 506 with a remainder of 0.
When the remainder is 0, the power is equivalent to i^4, which is 1.
So, i^2024 = (i^4)^506 = 1^506 = 1.
The value of the expression is 1.