For this case we have that a quadratic equation is of the form:
a: is the main coefficient because it accompanies the quadratic variable.
b: It is the linear coefficient
c: It is the constant term.
Then, a quadratic function with a main coefficient of "3" and a constant term of "-12" is:
Leading term: A
Constant term: C
f(x) = 3x^2 + 11x – 12