x^2-12x+39=0
The y-intercept occurs when x=0, so in this case it is (0, 39), y=39
There are no restrictions upon x so the domain is all real numbers, or if you prefer...x=(-oo,+oo).
dy/dx=2x-12 and d2y/d2x=2
Since acceleration is always a positive 2, when velocity is equal to zero, y is at an absolute minimum...
dy/dx=0 only when 2x-12=0, 2x=12, x=6
y(6)=36-72+39=3
So the minimum y is 3 and y increases without bound as x approaches ±oo.
This means that the range is y=[3, +oo)
