Question

Which of the following equations have complex roots?

Answer 1

9514 1404 393

Answer:

  B.  3x² +2 = 0

Step-by-step explanation:

The equation of A has a couple of real roots. We're pretty sure there are complex numbers that will satisfy this equation, but we don't know how to find them. (We suspect a typo, and that the equation is supposed to be 2x² +1 = 7x, which has only real roots.)

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The equation of B can be rewritten as ...

  x² = -2/3

This will have complex roots.

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The discriminants of both equations C and D are positive, so those have only real roots.

  2x² -5x -1   ⇒   d = (-5)² -4(2)(-1) = 33

  3x² -6x -1   ⇒   d = (-6)² -4(3)(-1) = 48