Drawing from Standard Form

To draw a parabola given in standard form, find the vertex first, then use a to place a second point. Take y = x^2 + 2x - 3. The axis is x = -2/(2 × 1), which is -1, and the height there is 1 - 2 - 3, which is -4. The vertex is (-1, -4).

Now the second point. As with vertex form, one step to the side of the vertex the curve moves by a. Here a is 1, so one step right, at x = 0, the height is -4 + 1 = -3. That gives (0, -3).

There is a free check: at x = 0 every term with x vanishes, so the curve meets the y-axis at c. Here c is -3, which matches the point just found. If a were 2, one step from the vertex the curve would rise 2 instead.