A Desmos table evaluates a function at the x-values you care about, which is faster than plugging each one in by hand. The calculator is covered in Desmos on the ACT.
Function values
Type y = the function, then add a table. Put the x-values from the question in the first column. The second column fills in. That is the move when a question asks for f(3), or which x makes y = 0, and the algebra is messy. Function notation on the test is in function notation.
Points you already have
If the question gives you a scatter of points, the same table is the start of a regression. That next step is in regression in Desmos. Reading a printed chart without typing it is in charts and tables.
The bottom line
Enter the function, drop the x-values into a table, and read the outputs. Use that list instead of four separate substitutions.
Start practicing
Start with a free diagnostic, then drill your weak spots with 15-question quizzes and track how you're doing across Reading, English, and Math. Compare plans whenever you're ready to go further.
This article offers general ACT prep guidance. The ACT can change from year to year, including its format, scoring, policies, test dates, and fees, so always confirm the latest details on the official ACT website at act.org before you make decisions. ACT® is a registered trademark of ACT, Inc. thirty-six is not affiliated with, endorsed by, or sponsored by ACT.