The quadratic formula is
.
From the problem, a is 1, b is -1, and c is 12. Plugging in these values gives:

Because there is a square root of a negative number, there is no solution.
1.28 = 128 * 10^-2
128 * (1/10^2)
128 / 10^2
128 / 100
1.28
Because, it's literally the same thing mathematically if you worked it out. Though, as I'm sure you're aware, it's just a much shorter and cleaner way of writing out large or small numbers.
I think 12 might be the second one, I'm not sure though!