Learning Resources

Investigation 1: Total Earnings & Focus A: Combination by Subtraction

Example: Given f(x) = 2x + 1 and g(x) = 3x. Graph f(x) + g(x).

• Press Y = and enter the equations for the two given functions. One equation will be in Y₁ position and the other in the Y₂ position.
• The Y₃equation will be the sum of these two functions, so scroll down to it. 
•  Press VARS and scroll over to Y-VARS. Select option 1: Function by pressing ENTER. 
• Now select Y₁ by hitting ENTER. 
• Press +
• Press VARS. Scroll over to Y-VARS.
•  Hit ENTER to select the Function option. 
• Scroll down to select Y₂.
•  Hit ENTER.
• Your screen should look as follows:

If you only want to view the graph of Y₁ + Y₂, you can put the cursor on the equal sign of each of the other equations and press enter to deselect them. The graph should look like the following: 

As expected, the graph of f(x) + g(x) is linear. Note also that the y-intercept is 1. This makes sense because f(0) + g(0) = 1. As well, since there is no restriction on the domains of f(x) and g(x), the domain of f(x) + g(x) is also the set of all real numbers.