Transformations
Effects of "a"
When the a-value is greater than one, the parabola becomes narrower. When the a-value is less than one, the parabola becomes wider. When the a-value is positive, the parabola will open upward; when it is negative the parabola will open downward.
Example The graph below represents the function
in blue and 
in red. Since both a -values are positive, the parabolas open up. Since 5 > 2, the blue parabola will be narrower than the red parabola.
Example The graph below represents the function
in blue and in red. Since both a -values are positive, the parabolas open up. Since 5 > 2, the blue parabola will be narrower than the red parabola.