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Find the roots of the equation z4 = 1 and select the correct option.

Mathematics

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Step-by-step solution

5 steps
  1. Rewrite the equation.

    The given equation is z4=1z^4 = 1.
    We can rewrite this as z4−1=0z^4 - 1 = 0.

  2. Factor the equation using the difference of squares formula, a2−b2=(a−b)(a+b)a^2 - b^2 = (a-b)(a+b).

    Here, a=z2a = z^2 and b=1b = 1.

    (z2)2−12=0(z^2)^2 - 1^2 = 0 (z2−1)(z2+1)=0(z^2 - 1)(z^2 + 1) = 0
  3. Factor each term further.

    The first term, z2−1z^2 - 1, is another difference of squares:

    z2−1=(z−1)(z+1)z^2 - 1 = (z-1)(z+1)

    The second term, z2+1z^2 + 1, can be factored using the imaginary unit ii, where i2=−1i^2 = -1:

    z2+1=z2−(−1)=z2−i2=(z−i)(z+i)z^2 + 1 = z^2 - (-1) = z^2 - i^2 = (z-i)(z+i)
  4. Combine the factors to find all roots.

    Substituting the factored terms back into the equation:

    (z−1)(z+1)(z−i)(z+i)=0(z-1)(z+1)(z-i)(z+i) = 0

    Setting each factor to zero gives the distinct roots:
    z−1=0  ⟹  z=1z-1 = 0 \implies z = 1
    z+1=0  ⟹  z=−1z+1 = 0 \implies z = -1
    z−i=0  ⟹  z=iz-i = 0 \implies z = i
    z+i=0  ⟹  z=−iz+i = 0 \implies z = -i

    The four distinct roots are 1,−1,i,−i1, -1, i, -i.

  5. Compare the roots with the given options.

    A. (1,−1,i,2i)(1, -1, i, 2i)
    B. (3,2,1,−2)(3, 2, 1, -2)
    C. (1,−1,i,−i)(1, -1, i, -i)
    D. (i,−2i,−3i,−4i)(i, -2i, -3i, -4i)

    The calculated roots match option C.

    The final answer is C. (1,−1,i,−i)\boxed{\text{C. } (1, -1, i, -i)}.

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