SAT Math tools

How to Use Desmos on the Digital SAT

Use Desmos to make a mathematical decision, not just a graph. Start with what the question asks, enter the relationship, and check that the output answers that exact question.

See worked examples Open testing calculator

Graph the relationshipCheck the resultReviewed September 4, 2026

Quick answer

Can you use Desmos on both SAT Math modules?

Yes. Bluebook includes graphing and scientific calculators throughout Math. Practice with the College Board testing version; it is configured differently from the general Desmos website. Calculator use is not allowed in Reading and Writing. See College Board's calculator policy.

Before you graph

What should you enter in Desmos?

Identify the requested quantity: an x-value, a y-value, an ordered pair, or a parameter. Those are different answers.
Enter each equation on a separate expression line. Keep parentheses around a complete numerator, denominator, or exponent.
Choose a sensible window. Check the scale against the values in the problem, then select a curve to reveal points of interest.
Verify the result in the original equation and context. An excluded denominator value or a negative length is not a valid answer just because it appears on screen.

Dolphin question-bank walkthroughs

How do you turn a graph into an answer?

These walkthroughs use the relationships in Dolphin bank questions 638, 1028, 626, 963, and 741, reviewed September 4, 2026. Follow the skill links for the complete practice questions. Try the method before revealing the check.

Roots and window settingsQuestion 638

Find an x-intercept without missing the graph

For $f (x) = x^{2} - 18 x - 360$ , an x-intercept is a point where $f (x) = 0$ .

Enter: y=x^2-18x-360

Show calculator steps and check

The default window may hide the useful part of this graph. In Graph Settings, try x from -20 to 40 and y from -500 to 100.
Select the parabola, then its x-axis crossings. The intercepts are (-12, 0) and (30, 0).
The question asks for an intercept, not the minimum. Of the listed answer choices, (-12, 0) is correct.

Check $(- 12)^{2} - 18 (- 12) - 360 = 144 + 216 - 360 = 0$ . Factoring gives $(x + 12) (x - 30)$ , confirming both roots.

Systems of equationsQuestion 1028

Distinguish no solution from infinitely many

One equation is $2 x + 6 y = 10$ . The task is to choose a second equation that makes the system have no solution.

Enter on separate lines: 2x+6y=10 and the candidate x+3y=-20.

Show calculator steps and check

The two graphs are distinct parallel lines. They have no common point, so this candidate produces no solution.
Verify with algebra: the first equation is $y = - x /3 + 5/3$ ; the candidate is $y = - x /3 - 20/3$ . The slopes match and the intercepts differ.
The tempting candidate $x + 3 y = 5$ is the first equation divided by 2. Its graph lies on the same line, giving infinitely many solutions instead.

Common trapNot seeing a crossing in one window does not prove two arbitrary graphs never meet. The slope-and-intercept check establishes the result here.

Choose the shorter methodQuestion 626

When is algebra quicker than Desmos?

For $f (x) = (x + 6) (x - 4)$ , the question asks for the x-coordinate of an x-intercept. The factors already reveal the answer.

Show the algebra-first solution

At an x-intercept, $y = 0$ , so $(x + 6) (x - 4) = 0$ .
Set each factor to zero: $x = - 6$ or $x = 4$ . Of the listed choices, $- 6$ is correct.
You can graph y=(x+6)(x-4) to check, but typing adds work once you recognize the zero-product rule.

Check the requested formEnter -6 for an x-coordinate. The ordered pair (-6, 0) answers a different wording.

Graph both sidesQuestion 963

Which coordinate solves the equation?

Solve $\frac{1}{4} (x + 5) - \frac{1}{3} (x + 5) = - 7$ . Graphing both sides makes a solution visible as an intersection.

Enter on separate lines: y=(x+5)/4-(x+5)/3 and y=-7.

Show calculator steps and check

Use Graph Settings to show x from 0 to 100 and y from -10 to 2. The intersection is outside a typical default window.
Select the intersection (79, -7). The equation asks for x, so the answer is 79, not -7.
Substitute: $(79 + 5) /4 - (79 + 5) /3 = 21 - 28 = - 7$ .

Algebra checkCombine the repeated factor: $(1/4 - 1/3) (x + 5) = - (x + 5) /12 = - 7$ . Then $x + 5 = 84$ , so $x = 79$ .

Common trapA point has two coordinates. Read the quantity requested before transferring a calculator result.

Domain restrictionsQuestion 741

Can a graph hide an undefined value?

For $f (x) = \frac{2 x ^{2} - 8 x + 6}{x - 3}$ , find the x-value where the function is undefined. The denominator is the decisive information.

Enter: f(x)=(2x^2-8x+6)/(x-3). Then evaluate f(3).

Show calculator steps and check

Before graphing, record $x - 3 \neq = 0$ , so $x \neq = 3$ . The function is undefined at $x = 3$ .
Factor the numerator: $2 x^{2} - 8 x + 6 = 2 (x - 1) (x - 3)$ . Canceling gives $2 (x - 1)$ only when $x \neq = 3$ .
The graph follows the line y=2x-2 away from x=3. At ordinary zoom, the missing point (3, 4) may not be obvious. Evaluating f(3) from the original expression is undefined.

CheckAt $x = 3$ , the original fraction is $0/0$ , not 4. Cancellation does not restore a value excluded by the original denominator.

Common trapA simplified graph can conceal a restriction. For a question about where a function is undefined, checking the denominator is faster and more reliable than inspecting pixels.

Try the method

College Board graphing calculator

Open the calculator in its own tab for more space.

Paired data

How do you enter a regression for SAT practice?

Use Add Item, then Table. Put each x-value and its matching y-value in the same row. A copied column with one shifted row changes the data.
Choose the model the question specifies. For a linear model, enter y_1 ~ m x_1 + b on a new expression line. Use a tilde, not an equals sign.
Read the fitted m and b values, then interpret their units. The slope is the change in predicted y per unit increase in x, not necessarily the requested final answer.
Substitute the requested x into the fitted model if a prediction is required. Keep precision until the final rounding step and be cautious outside the observed data range.

Regression fits a model; it does not establish causation or decide which model is appropriate. See Desmos's regression guidance. The testing calculator automatically enables Log Mode for applicable exponential, logarithmic, and power regressions, so generic online tutorials may differ from test-day behavior. Testing configuration.

SAT Desmos tips

When should you stop and use another method?

Unknown parameters need reasoning

A slider shows particular cases, not a proof that a statement holds for every value. For a condition such as exactly one solution, reason about slopes, discriminants, or the structure of the equation.

Decimals can hide the exact answer

Do not round a displayed decimal early and build the rest of the solution on it. Preserve exact fractions or radicals with algebra when the question requires them.

A graph can hide a restriction

Record excluded values before canceling a factor in a rational expression. A tiny hole may not be obvious in a graph; the original denominator still controls the domain.

Practice the underlying math

Build a method you can check

Primary sources

Official calculator guidance

SAT Suite Calculator PolicyCollege Board
Find the College Board testing calculatorDesmos
College Board calculator configuration, 2026-2027Desmos
Assessment resources and calculator FAQDesmos
How regression works in DesmosDesmos

Calculator FAQ

Questions about Desmos on the SAT

Can you use Desmos on the entire SAT Math section?

Yes. The embedded calculator is available throughout SAT Math, including both modules. It is not available for Reading and Writing. You can switch between graphing and scientific calculators in Bluebook.

Which Desmos calculator should I practice with for the SAT?

Use the College Board version linked from the Desmos testing page, and rehearse with the embedded calculator in Bluebook. The ordinary Desmos website can include features that are unavailable on the test.

Can Desmos solve every SAT Math question?

No. It can evaluate and graph the expressions you enter, but you must model the problem, choose the relevant result, and check restrictions. A graph also cannot prove an algebraic identity just because two curves appear to overlap.

Why does my Desmos graph show no intersection?

Check your entries and the viewing window before concluding there is no solution. An intersection may be outside the visible area. For linear systems, compare slopes and intercepts to establish whether the lines are parallel, intersecting, or identical.

Do I need regression for every equation on the SAT?

No. Use regression when you need to fit a specified type of model to paired data. For a simple equation, graphing both sides or solving algebraically is usually a more direct approach.