>>8
You're right, we want an A that makes the c (as in ax^2+bx+c) become 120
the C will be -((38/3.6)^2 * (g/240))*A
being that we want that to be 120, A = -120/((38/3.6)^2 * (g/240))
so de correct equation is
y = -120/((38/3.6)^2 * (g/240))*(x - (38/3.6)*sqrt(g/240)) * (x + (38/3.6)*sqrt(g/240))