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Question

What is \((1+i)^4 + (1-i)^4\) equal to, where \(i = \sqrt{-1}\)?

This question was previously asked in
NDA 2 2024 GAT Question Paper (01-Sep-2024)
The correct answer is
-8

Calculating \((1+i)^4 + (1-i)^4\)

This problem involves calculating the sum of powers of complex numbers. We need to find the value of the expression \((1+i)^4 + (1-i)^4\), where the imaginary unit \(i\) is defined as \(\sqrt{-1}\).

Evaluating \((1+i)^4\)

We can evaluate \((1+i)^4\) in a couple of ways. One common method is to first calculate \((1+i)^2\).

  • \((1+i)^2 = 1^2 + 2(1)(i) + i^2\)
  • Since \(i^2 = -1\), this becomes \(1 + 2i - 1\).
  • Simplifying, we get \((1+i)^2 = 2i\).

Now, we can find \((1+i)^4\) by squaring the result of \((1+i)^2\):

  • \((1+i)^4 = ((1+i)^2)^2\)
  • Substituting the value we found: \((1+i)^4 = (2i)^2\).
  • Squaring this gives \(4i^2\).
  • Again, since \(i^2 = -1\), we have \(4(-1)\).
  • Therefore, \((1+i)^4 = -4\).

Evaluating \((1-i)^4\)

Similarly, we evaluate \((1-i)^4\). First, let's find \((1-i)^2\).

  • \((1-i)^2 = 1^2 - 2(1)(i) + i^2\)
  • Substituting \(i^2 = -1\): \(1 - 2i - 1\).
  • Simplifying, we get \((1-i)^2 = -2i\).

Now, we find \((1-i)^4\) by squaring \((1-i)^2\):

  • \((1-i)^4 = ((1-i)^2)^2\)
  • Substituting the value we found: \((1-i)^4 = (-2i)^2\).
  • Squaring this gives \(4i^2\).
  • Since \(i^2 = -1\), this is \(4(-1)\).
  • Therefore, \((1-i)^4 = -4\).

Summing the Results

Finally, we need to add the results of \((1+i)^4\) and \((1-i)^4\) together.

  • The expression is \((1+i)^4 + (1-i)^4\).
  • Substituting the values we calculated: \((-4) + (-4)\).
  • The sum is \(-8\).

Conclusion

The value of \((1+i)^4 + (1-i)^4\) is \(-8\). This corresponds to the option provided.

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Similar Questions

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Important Questions from Complex Numbers

  1. If \(x + iy = \sqrt {\frac{{a + ib}}{{c + id}}}\), then the value of x2 + y2 is -

  2. If x = cos θ + i sin θ, then the value of \({x^n} + \frac{1}{{{x^n}}}\) is:

  3. If \(\left| {\begin{array}{*{20}{c}} {6i}&{ - 3i}&1\\ 4&{3i}&{ - 1}\\ {20}&3&i \end{array}} \right| = x + iy\), then the values of x and y are:

  4. If iz3 + z2 - z + i = 0, then the value of |z| is:

  5. Nature of the triangle formed by the points representing the complex numbers 3 + 4i, 8 - 6i and 13 + 9i is:

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