Question

Solve 3x2 = -12x - 15.
Ox= -4 + 2i
Ox=-4+1
Ox=-2 + 2i
Ox= -2

Answer 1

x = -2 - i, -2 + i.

Explanation:

3x2 = -12x - 15

3x^2 + 12x + 15 = 0

Divide through by 3:

x^2 + 4x + 5 = 0

x^2 + 4x = -5

Completing the square:

x^2 + 4x + 4 = -5 + 4

(x + 2)^2 = -1

x + 2 = √-1 = i

x = -2 - i, -2 + i.