Understanding Quadratic Functions
When you see a quadratic function written as ax² + bx + c = 0 (where a≠0), you can quickly identify several important features. The line of symmetry is a vertical line that perfectly divides the parabola into two mirror images, found using x = -b/(2a).
The vertex is the lowest point (when a>0) or highest point (when a<0) of the parabola. This critical point falls right on the line of symmetry and has coordinates −b/(2a),f(−b/(2a)). The y-intercept is simply the point where the parabola crosses the y-axis, which equals c.
Quick Tip: To remember the vertex formula, think "opposite of b divided by 2a" for the x-coordinate. Then plug that x-value back into the original equation to find the y-coordinate.
Another useful way to write quadratic functions is in vertex form: y = ax−h² + k, where (h,k) is the vertex. This form makes it super easy to spot the vertex without calculations, and the axis of symmetry is always x = h.