You can graph a high school function without assembling the pair table (x, y), but just by following the following observation script:
The value of the coefficient The defines the concavity of the parable;
Zeros define the points at which the parable intersects the x axis;
The vertex V indicates the minimum (if a> 0), or maximum (if <0) point;
The line passing through V and parallel to the y axis is the axis of symmetry of the parable;
For x = 0, we have y = a · 02 + b · 0 + c = c; then (0, c) is the point at which the parable cuts the y axis.