For a parabola in standard form (y = ax^2 + bx + c), use (x = -frac{b}{2a})
For a parabola in vertex form (y = a(x-h)^2 + k), use (x = h)
For a parabola in factored form (y = a(x-r_1)(x-r_2)), use (x = frac{r_1 + r_2}{2})
For a graph, draw a vertical line through the vertex
For a table of values, find the x-values with equal y-values and take the midpoint
For a symmetric shape, identify the line that divides it into two matching halves