Question: how to find the roots of a function on a graphing calculator?
Answer: Press Graph.
Press More and then Math (F1)
Press Lower (F1). Arrow to the left of the x-intercept and press enter.
Press Upper (F2). Arrow to the right of the x-intercept and press enter.
Press Root (F3). ... 
The TI-85 will return a value for x and 0 (or really close to it) for y.