5 Desmos tricks for the Digital SAT

Short answer: the Digital SAT gives you a Desmos graphing calculator on every math question. Graph both equations and tap the intersection to solve a system; use ~ for line-of-best-fit; add a slider for "for what value of k"; count x-axis hits to count solutions; and use a table to test answer choices.

1. Intersect to solve a system

Graph both equations and tap the point where they cross. That point is the solution (x, y).

→ tap the crossing: (2, 7)

2. Regression for "line of best fit"

Put the data in a table, then use a tilde (~) to make Desmos find the best-fit slope and intercept.

→ read m and b off the results

3. Sliders for "for what value of k"

Type the equation with k, add the slider, and drag until the graph does what the question describes.

→ exactly one solution when the vertex touches the x-axis: k = 9

4. Graph to count solutions

Number of real solutions = number of times the graph hits the x-axis (or the other graph).

→ never touches the x-axis: 0 real solutions

5. Table to test answer choices

Define the function, add a table, and type each answer choice as an x value. The one that gives 0 (or the target) wins.

→ table x = 2, 3: f(3) = 0, so 3 is a solution