Question

I need help on number 9

Answer 1

3. -1/3 ± 2i√5 / 3

Explanation:

3x^2 + 2x = -7

Divide through by 3:

x^2 + 2/3 x = -7/3

Completing the square:

x^2 + 2/3 x + (1/3)^2 = -7/3 + (1/3)^2

(x + 1/3)^2 = -7/3 + 1/9

(x + 1/3)^2 = -20/9

x + 1/3 = ±√(-20) / 3

x + 1/3 = ± 2√-5/3

x = -1/3 ± 2i√5 / 3