12x^2+6x-6. how to find the vertex of this equation using (-b/2a)

Solve for x over the real numbers:
6 (2 x^2 + x - 1) = 0

Divide both sides by 6:
2 x^2 + x - 1 = 0

The left hand side factors into a product with two terms:
(x + 1) (2 x - 1) = 0

Split into two equations:
x + 1 = 0 or 2 x - 1 = 0

Subtract 1 from both sides:
x = -1 or 2 x - 1 = 0

Add 1 to both sides:
x = -1 or 2 x = 1

Divide both sides by 2:

x = -1 or x = 1/2

It’s hard to understand what you put.. can you show a picture ?