Math CentralQuandaries & Queries


Question from Ashini, a student:

The inverse function for f(x)=2x^2+5x

Hi Ashini,

The first thing I would is plot $y = 2x^2 + 5x$ as I did in my response to a similar question. I then relabeled the X-axis as Y and the Y-axis as X and put the graph in standard position with the new X-axis horizontal and the Y-axis vertical I get


Thus you can see that the inverse is composed of two functions, one that is the top half of the parabola and the other the bottom half of the parabola.

To find an expression for these functions use the technique suggested by RD.

Write back if you need further assistance,

About Math Central


Math Central is supported by the University of Regina and the Imperial Oil Foundation.
Quandaries & Queries page Home page University of Regina