In mathematical terms, the equation that represents a graph line is expressed as "Y = AX + B." If you have graphed a line on your TI84 graphing calculator, you don't actually have to perform separate mathematical equations in order to find the equation that represents this line. You can find the equation of a line on your TI84 in just a couple of buttonpresses.

Press "Stat" on your TI84 calculator.

Select the "Calc" option.

Choose the "LinReg" (short for "Linear Regression") option on screen.

Select the "Enter" key. This will provide you with the values for "A" and "B" in the line you graphed on your calculator.

Plug the numbers you just calculated into the "y= ax + b" equation. For example, if the TI84 told you that "A=50" and "B=20", the equation that represents the line would be "y= 50x + 20."