How to Use Desmos on the SAT: 5 Moves That Save Time

Desmos is available for the whole SAT Math section. It doesn't replace knowing the math, because you still have to know what to type. But for many questions, it's quicker and safer than doing the algebra by hand.

Move 1: Solve an equation by graphing both sides

Worked examples

$3 (x - 2) + 1 = 2 x + 4$

Type each side as its own line. $y = 3 (x - 2) + 1$ and $y = 2 x + 4$

Tap the intersection. Its $x$ value is the answer. $x = 9$

Move 2: Solve a system

Type both equations just as they're written. Desmos accepts forms like $3 x + 2 y = 12$ . The intersection is the solution, and parallel lines mean there's no solution.

Move 3: Read a parabola

Find the minimum of $y = x^{2} - 6 x + 11$ .

Type it, and tap the lowest point. $(3, 2)$

So.The minimum value is 2

Move 4: Use a slider for an unknown constant

If a question has a constant $k$ , type the equation with $k$ in it, and Desmos offers a slider. Move it until the graph does what the question describes, such as touching the $x$ -axis once. This is a fast way to handle many discriminant questions.

Move 5: Test the answer choices

When a question asks which expression is equivalent, graph the original and each choice. The right one lands exactly on top of the original.

When not to use it

Some questions are quicker by hand, such as $3 x + 5 = 20$ . And Desmos won't tell you what a number means in a word problem. Practice both ways, so you know which is faster for you.