How to Use Desmos on the Digital SAT (5 Time-Saving Tricks)
Desmos is built into Bluebook, the official Digital SAT app. Used well, it cuts your problem-solving time in half on many Math questions. Here are five tricks that move the needle.
Quick answer
Type any equation directly to graph it. Type “x =” or “y =” to solve. Click intersections of two curves to read coordinates. Use sliders for “what value of k…”. Use table mode for input/output questions.
Trick 1 — Type the equation to graph it
For “find x where y = x² – 4x – 5 = 0,” just type “x² – 4x – 5 = 0” into Desmos. It instantly shows x = -1 and x = 5. No quadratic formula needed.
Trick 2 — Find intersections by clicking
Type both curves. Click where they cross. Desmos reads off the (x, y) coordinates automatically.
Trick 3 — Use sliders for “find the value of k”
When the question asks “for what value of k does the equation have one solution,” type the equation using k, then add “k = 1” on a new line. Desmos creates a slider. Drag k until the conditions match.
Trick 4 — Table mode for input-output
When given a function and asked to evaluate at several points, type the function then add a table. Desmos fills in y for every x.
Trick 5 — Use brackets for piecewise functions
For piecewise functions, use brackets like {x < 2: x², x >= 2: 2x}. Desmos graphs each piece correctly.
Common mistakes
- Not using Desmos at all (most students try algebra first).
- Trying to solve word problems with Desmos before setting up the equation.
- Forgetting Desmos uses ^ for exponents and * for multiplication.