Correct Answer - Option 3 : 3

__Concept:__

The roots of a quadratic equation ax2 + bx + c = 0 is give by:

\(\rm x = {-b ± \sqrt{b^2-4ac} \over 2a}\)

The discriminant of the equation is D = b2 - 4ac

- D > 0, roots are unequal and real
- D < 0, roots are imaginary
- D = 0, roots are real and equal

__Calculation:__

Given quadratic equation:

ax2 + 12x + 12 = 0

a = a, b = 12 and c = 12

∵ Roots are real and equal, D = 0

b^{2} - 4ac = 0

12^{2} - 4 × a × 12 = 0

144 = 48a

**a = 3**