Write the quadratic in standard form: (f(x)=ax^2+bx+c)
Determine whether the parabola opens upward or downward by checking the sign of (a)
Find the vertex using (x=-frac{b}{2a})
Substitute the vertex (x)-value into the function to get the vertex (y)-value
If (a>0), the range is (y geq) vertex (y)-value
If (a<0), the range is (y leq) vertex (y)-value
Write the range in interval notation
For (a>0), use ([text{vertex } y,infty))
For (a<0), use ((-infty,text{vertex } y])