In the graph below, find the axis of symmetry.
First, we need to consider what the axis of symmetry is in a parabola. It’s the vertical line that divides the parabola into two congruent halves. If the quadratic function is written in standard form, then the axis of symmetry is equal to the vertical line 𝑥 equals negative 𝑏 over two 𝑎.
However, in this graph, we just need to visually inspect to find the axis of symmetry. This line divides the parabola in half. At a height of nine, the parabola is three units away on the right and three units away on the left. The line that divides this parabola in half, its axis of symmetry, is the 𝑦-axis.