Which polynomial equations have - i as one of their roots?

1. x^3 + 5x^2 - 20 = 0

2. x^3 - x^2 + x - 1 = 0

3. x^3 + 3x^2 + x + 3 = 0

4. x^3 - 2x^2 + x - 2 = 0

5. x^3 - 6x^2 - 16x + 96 = 0

Question

Mathematics

Eden Dixon

19 January, 22:12

Which polynomial equations have - i as one of their roots?

1. x^3 + 5x^2 - 20 = 0

2. x^3 - x^2 + x - 1 = 0

3. x^3 + 3x^2 + x + 3 = 0

4. x^3 - 2x^2 + x - 2 = 0

5. x^3 - 6x^2 - 16x + 96 = 0

+1

Answers (1)

Know the Answer?

Antony Finley · Answer 1

I = sqrt (-1)

i^2 = - 1

(-i) ^2 = (-i) (-i) = i^2 = - 1

(-i) ^3 = (-i) (-i) (-i) = (-i) (i^2) = i

use these facts to find which equation is correct if x = - i

i bet on 2,3 or 4

Which polynomial equations have - i as one of their roots?1. x^3 + 5x^2 - 20 = 02. x^3 - x^2 + x - 1 = 03. x^3 + 3x^2 + x + 3 = 04. x^3 - 2x^2 + x - 2 = 05. x^3 - 6x^2 - 16x + 96 = 0

Which polynomial equations have - i as one of their roots?

1. x^3 + 5x^2 - 20 = 0

2. x^3 - x^2 + x - 1 = 0

3. x^3 + 3x^2 + x + 3 = 0

4. x^3 - 2x^2 + x - 2 = 0

5. x^3 - 6x^2 - 16x + 96 = 0