Answer: ±2i.
- A ±2
- B ±2i
- C ±4i
- D ±i√2
Correct answer: B. ±2i
Explanation: sqrt(-4) = sqrt(4 x (-1)) = 2i. Square roots of -4 are +2i and -2i.
A complex number z = a+ib is plotted as a point (or vector from the origin) on the Argand plane, with the real part along the horizontal axis and the imaginary part along the vertical; its modulus |z| is the vector's length, and its argument θ is the angle from the positive real axis.
Concept context
Complex numbers in a+ib form, modulus, argument, polar form, cube roots of unity, and quadratic equations with complex roots
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