Answer:
x = -3 + i√6 and x = -3 - i√6
Explanation:
Let's apply the "completing the square" method to find the roots of this equation.
Take half of the coefficient 6 of x, square it and add this result to x^2 + 6x. Then subtract the same quantity:
x^2 + 6x + 15 becomes
x^2 + 6x + 3^2 - 3^2 + 15 = 0
Rewriting the first three terms as the square of a binomial, we ge:
(x + 3)^2 - 9 + 15 = 0, which simplifies to:
(x + 3)^2 + 6 = 0, or (x + 3)^2 = -6
Taking the square root of both sides:
x + 3 = ±i√6
Then the two roots are complex:
x = -3 + i√6 and x = -3 - i√6