Digital SAT® Desmos Calculator Guide: 10 Secret Hacks for 800

Trick 1: Solving Any System of Equations in 3 Seconds

Whenever an SAT problem asks for the solution $(x, y)$, the number of solutions, or the value of $x+y$ for a system:

1. Type Equation 1 directly into Line 1 (e.g., $3x - 4y = 12$).
2. Type Equation 2 directly into Line 2 (e.g., $y = x^2 - 4x + 1$).
3. Click on the gray intersection points. Desmos automatically displays the exact coordinates $(x, y)$.

Trick 2: Using Sliders for Unknown Constants ($c$, $k$)

When the question asks: "For what value of $c$ does the equation $x^2 + 6x + c = 0$ have exactly one real solution?"

1. Type $y = x^2 + 6x + c$ into Desmos.
2. Click "add slider: c".
3. Slide $c$ until the vertex of the parabola touches the $x$-axis exactly once. You will immediately see $c = 9$.

Trick 3: Instant Min / Max & Vertex Identification

Word problems about maximum profit, minimum height, or peak trajectory can be graphed immediately:

• Type the quadratic function $h(t) = -16t^2 + 64t + 80$.
• Click on the highest point (vertex). Desmos highlights the point with a gray dot: $(2, 144)$.
• Interpret directly: Maximum height is $144$ feet at time $t = 2$ seconds.

Trick 4: Testing Equivalent Expressions with Regressions

When an algebraic expression asks: "Which of the following is equivalent to $\frac{x^2 - 9}{x - 3}$?"

1. Type the original expression into Line 1: $y_1 = \frac{x^2 - 9}{x - 3}$.
2. Type the answer choices into Line 2, 3, 4, 5.
3. The correct answer choice will graph an identical line that lies perfectly on top of the original function.

Frequently Asked Questions