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To arithmetically combine two graphs: 
- Shift-click the bar at the left end of each graph to select the graph. The graph you click first is A, the graph you click second is B.
- Use one of the four Combine buttons in the Advanced portion of the Graph Adjuster tab labeled A+B, A-B, A*B, and A/B.
- Alternatively, right-click the bar at the left end of either graph and choose Combine Graphs, then choose one of the following:
- Create Sum Graph (A+B)
- Create Difference Graph (A-B)
- Create Product Graph (A*B)
- Create Ratio Graph (A/B)