Every math question on the Digital SAT comes with a graphing calculator built into Bluebook, and it's Desmos. You can use it on the whole math section. Most people only use it as a regular calculator, which wastes the best part. These are the tricks that save the most time, with the exact thing to type for each one.
1. Solve an equation by typing it as-is
Type the equation exactly as it's written, like 4x-15=17. Desmos draws a vertical line at the answer. Tap the line and it shows x = 8. No moving terms around, no sign mistakes.
2. Systems of equations: tap where the lines cross
Type each equation on its own line, for example x+y=6 and x-y=-8. Tap the point where the lines cross and Desmos shows it, here (-1, 7). The first number is x and the second is y. This works for any system of two equations, even ugly ones with fractions.
3. Quadratics: read the x-intercepts
Type the equation as a graph, like y=x^2-6x+5. The solutions are where the curve crosses the x-axis, so tap those two points: x = 1 and x = 5. If they ask for the sum or product of the solutions, you now have both. Tap the lowest or highest point of the curve for the vertex.
4. "No solution" questions: use a slider
The SAT loves questions like "for what value of k does this system have no solution?" Type both equations with k in them. Desmos offers to add a slider for k, so accept it and drag. When the two lines go parallel and stop crossing, that value of k is your answer. Parallel lines never meet, which is exactly what "no solution" means.
Same idea for "infinitely many solutions": drag until the two lines sit right on top of each other.
5. Mean, median and more are built in
Skip the adding. Type mean(72,81,90,64,88) or median(41,12,33,58,20) and Desmos does it. It also knows stdev() if a question is comparing spread.
6. Check "which expression is equivalent" by plugging in a number
If you forget an exponent rule, pick a value and test it. For a question about x3 · x4, type 2^3*2^4, then try each answer choice with 2 in place of x, like 2^7. The choice that gives the same number is right.
7. Percents, the easy way
Desmos understands percent words. 20% of 300 gives 60, and 260-25% of 260 gives 195. For "up 20% then down 20%" questions, type 100*1.2*0.8 and you'll see it ends at 96, not 100.
When not to use Desmos
If a question takes one or two quick steps by hand, typing it in usually takes longer. Simple percents, angle sums and plugging into a formula you know are often faster on scrap paper. Desmos earns its time on systems, quadratics, anything with a "for what value" and anything where a sign slip is likely.
The best way to get fast is to practice with it before test day, so the typing becomes automatic.
Practice this in Lock In
Ten questions a day, picked from what you keep missing, with a full explanation and the Desmos steps for every math question. Free, no email needed to start.