Window
TI-84: WINDOW → set Xmin/Xmax/Xscl and Ymin/Ymax/Yscl. Desmos: wrench icon → enter x/y bounds.
Common error: A poor window can hide an intercept or make two curves look tangent.
Calculator field guide
TI-84 first. Bluebook Desmos when it is the tool in front of you.
Use a graphing calculator for numerical intersections, regressions, awkward evaluations, and verification. Do not use it to replace algebra that the prompt asks you to show.
Regression
TI-84: STAT → EDIT → enter L1/L2 → STAT CALC → choose model. Desmos: enter a table, then y₁ ~ a·b^{x₁}.
Common error: Do not choose a model only because R² is visible; inspect residual pattern and context.
Intersection
TI-84: GRAPH → 2nd TRACE → intersect → select curves and give a nearby guess. Desmos: tap the plotted intersection.
Common error: Record which equations intersect and round only as requested.
Zero
TI-84: GRAPH → 2nd TRACE → zero → left bound, right bound, guess. Desmos: tap an x-intercept.
Common error: A zero is an input. Do not report the displayed point as an unexplained calculator answer.
Write calculator results into an FRQ
- Name the equation, model, or two functions used.
- Report the relevant input/output with requested precision and units.
- Interpret the result or connect it to the requested conclusion.
Never copy a screen value alone when the task asks you to justify, interpret, construct, or show work.